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	$62.52	5.349%	$65.8642	$65.86	$65.85	$65.90
Purchase #2	$28.64	10.198%	$31.5607	$31.56	$31.55	$31.60
Purchase #3	$82.76	9.479%	$90.6048	$90.60	$90.60	$90.60
Purchase #4	$10.45	3.463%	$10.8119	$10.81	$10.80	$10.80
Purchase #5	$28.73	8.328%	$31.1226	$31.12	$31.10	$31.10
Purchase #6	$90.40	7.319%	$97.0164	$97.02	$97.00	$97.00
Purchase #7	$42.39	13.563%	$48.1394	$48.14	$48.15	$48.10
7 purchase totals =	$345.89		$375.1200	$375.11	$375.05	$375.10