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	$50.55	8.224%	$54.7072	$54.71	$54.70	$54.70
Purchase #2	$35.62	5.581%	$37.608	$37.61	$37.60	$37.60
Purchase #3	$78.33	6.751%	$83.6181	$83.62	$83.60	$83.60
Purchase #4	$100.87	7.553%	$108.4887	$108.49	$108.50	$108.50
Purchase #5	$89.27	6.107%	$94.7217	$94.72	$94.70	$94.70
Purchase #6	$33.45	11.227%	$37.2054	$37.21	$37.20	$37.20
Purchase #7	$45.32	12.417%	$50.9474	$50.95	$50.95	$50.90
7 purchase totals =	$433.41		$467.2965	$467.31	$467.25	$467.20