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	$128.72	9.707%	$141.2149	$141.21	$141.20	$141.20
Purchase #2	$169.42	4.680%	$177.3489	$177.35	$177.35	$177.30
Purchase #3	$106.31	4.638%	$111.2407	$111.24	$111.25	$111.20
Purchase #4	$176.29	13.751%	$200.5316	$200.53	$200.55	$200.50
Purchase #5	$55.84	11.831%	$62.4464	$62.45	$62.45	$62.40
Purchase #6	$70.72	11.409%	$78.7884	$78.79	$78.80	$78.80
Purchase #7	$165.68	5.185%	$174.2705	$174.27	$174.25	$174.30
7 purchase totals =	$872.98		$945.8414	$945.84	$945.85	$945.70