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	$82.75	6.529%	$88.1527	$88.15	$88.15	$88.20
Purchase #2	$99.89	11.374%	$111.2515	$111.25	$111.25	$111.30
Purchase #3	$206.53	8.114%	$223.2878	$223.29	$223.30	$223.30
Purchase #4	$206.72	8.235%	$223.7434	$223.74	$223.75	$223.70
Purchase #5	$199.76	6.250%	$212.245	$212.25	$212.25	$212.20
Purchase #6	$158.43	7.239%	$169.8987	$169.90	$169.90	$169.90
Purchase #7	$138.93	5.486%	$146.5517	$146.55	$146.55	$146.60
7 purchase totals =	$1,093.01		$1,175.1308	$1,175.13	$1,175.15	$1,175.20