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	$212.76	3.354%	$219.896	$219.90	$219.90	$219.90
Purchase #2	$248.27	12.560%	$279.4527	$279.45	$279.45	$279.50
Purchase #3	$247.80	12.540%	$278.8741	$278.87	$278.85	$278.90
Purchase #4	$125.65	4.142%	$130.8544	$130.85	$130.85	$130.90
Purchase #5	$213.26	4.727%	$223.3408	$223.34	$223.35	$223.30
Purchase #6	$247.62	3.173%	$255.477	$255.48	$255.50	$255.50
Purchase #7	$231.66	3.771%	$240.3959	$240.40	$240.40	$240.40
7 purchase totals =	$1,527.02		$1,628.2909	$1,628.29	$1,628.30	$1,628.40