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	$133.28	13.551%	$151.3408	$151.34	$151.35	$151.30
Purchase #2	$70.65	6.822%	$75.4697	$75.47	$75.45	$75.50
Purchase #3	$221.30	10.309%	$244.1138	$244.11	$244.10	$244.10
Purchase #4	$185.53	5.770%	$196.2351	$196.24	$196.25	$196.20
Purchase #5	$150.47	5.154%	$158.2252	$158.23	$158.25	$158.20
Purchase #6	$36.57	3.251%	$37.7589	$37.76	$37.75	$37.80
Purchase #7	$227.48	12.862%	$256.7385	$256.74	$256.75	$256.70
7 purchase totals =	$1,025.28		$1,119.8820	$1,119.89	$1,119.90	$1,119.80