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	$190.48	13.488%	$216.1719	$216.17	$216.15	$216.20
Purchase #2	$143.67	5.736%	$151.9109	$151.91	$151.90	$151.90
Purchase #3	$221.68	8.538%	$240.607	$240.61	$240.60	$240.60
Purchase #4	$108.41	3.240%	$111.9225	$111.92	$111.90	$111.90
Purchase #5	$181.41	11.825%	$202.8617	$202.86	$202.85	$202.90
Purchase #6	$82.70	10.529%	$91.4075	$91.41	$91.40	$91.40
Purchase #7	$74.99	3.443%	$77.5719	$77.57	$77.55	$77.60
7 purchase totals =	$1,003.34		$1,092.4534	$1,092.45	$1,092.35	$1,092.50