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	$86.71	10.624%	$95.9221	$95.92	$95.90	$95.90
Purchase #2	$37.73	13.625%	$42.8707	$42.87	$42.85	$42.90
Purchase #3	$226.64	9.396%	$247.9351	$247.94	$247.95	$247.90
Purchase #4	$155.64	11.738%	$173.909	$173.91	$173.90	$173.90
Purchase #5	$106.53	4.429%	$111.2482	$111.25	$111.25	$111.20
Purchase #6	$43.26	7.400%	$46.4612	$46.46	$46.45	$46.50
Purchase #7	$42.98	4.151%	$44.7641	$44.76	$44.75	$44.80
7 purchase totals =	$699.49		$763.1104	$763.11	$763.05	$763.10