Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$150.49	13.768%	$171.2095	$171.21	$171.20	$171.20
Purchase #2	$245.26	4.405%	$256.0637	$256.06	$256.05	$256.10
Purchase #3	$54.48	4.222%	$56.7801	$56.78	$56.80	$56.80
Purchase #4	$47.47	10.323%	$52.3703	$52.37	$52.35	$52.40
Purchase #5	$144.73	10.804%	$160.3666	$160.37	$160.35	$160.40
Purchase #6	$118.63	4.450%	$123.909	$123.91	$123.90	$123.90
Purchase #7	$192.65	6.609%	$205.3822	$205.38	$205.40	$205.40
7 purchase totals =	$953.71		$1,026.0814	$1,026.08	$1,026.05	$1,026.20