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	$92.86	4.171%	$96.7332	$96.73	$96.75	$96.70
Purchase #2	$99.57	11.787%	$111.3063	$111.31	$111.30	$111.30
Purchase #3	$94.33	6.515%	$100.4756	$100.48	$100.50	$100.50
Purchase #4	$223.76	3.848%	$232.3703	$232.37	$232.35	$232.40
Purchase #5	$126.37	9.327%	$138.1565	$138.16	$138.15	$138.20
Purchase #6	$178.70	8.153%	$193.2694	$193.27	$193.25	$193.30
Purchase #7	$152.77	13.398%	$173.2381	$173.24	$173.25	$173.20
7 purchase totals =	$968.36		$1,045.5494	$1,045.56	$1,045.55	$1,045.60