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	$231.63	6.321%	$246.2713	$246.27	$246.25	$246.30
Purchase #2	$242.35	9.308%	$264.9079	$264.91	$264.90	$264.90
Purchase #3	$120.70	9.464%	$132.123	$132.12	$132.10	$132.10
Purchase #4	$229.38	11.700%	$256.2175	$256.22	$256.20	$256.20
Purchase #5	$137.37	13.276%	$155.6072	$155.61	$155.60	$155.60
Purchase #6	$191.71	9.422%	$209.7729	$209.77	$209.75	$209.80
Purchase #7	$193.38	3.759%	$200.6492	$200.65	$200.65	$200.60
7 purchase totals =	$1,346.52		$1,465.5490	$1,465.55	$1,465.45	$1,465.50