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	$91.46	7.823%	$98.6149	$98.61	$98.60	$98.60
Purchase #2	$58.48	4.400%	$61.0531	$61.05	$61.05	$61.10
Purchase #3	$57.57	10.268%	$63.4813	$63.48	$63.50	$63.50
Purchase #4	$185.66	13.512%	$210.7464	$210.75	$210.75	$210.70
Purchase #5	$41.26	3.141%	$42.556	$42.56	$42.55	$42.60
Purchase #6	$16.66	4.857%	$17.4692	$17.47	$17.45	$17.50
Purchase #7	$41.73	6.783%	$44.5605	$44.56	$44.55	$44.60
7 purchase totals =	$492.82		$538.4814	$538.48	$538.45	$538.60