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	$83.28	9.809%	$91.4489	$91.45	$91.45	$91.40
Purchase #2	$89.61	11.757%	$100.1454	$100.15	$100.15	$100.10
Purchase #3	$89.30	4.131%	$92.989	$92.99	$93.00	$93.00
Purchase #4	$111.30	12.794%	$125.5397	$125.54	$125.55	$125.50
Purchase #5	$116.27	12.123%	$130.3654	$130.37	$130.35	$130.40
Purchase #6	$7.77	6.400%	$8.2673	$8.27	$8.25	$8.30
Purchase #7	$179.83	3.165%	$185.5216	$185.52	$185.50	$185.50
7 purchase totals =	$677.36		$734.2773	$734.29	$734.25	$734.20