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	$124.35	13.753%	$141.4519	$141.45	$141.45	$141.50
Purchase #2	$152.82	11.379%	$170.2094	$170.21	$170.20	$170.20
Purchase #3	$103.64	7.430%	$111.3405	$111.34	$111.35	$111.30
Purchase #4	$182.39	9.711%	$200.1019	$200.10	$200.10	$200.10
Purchase #5	$44.30	8.118%	$47.8963	$47.90	$47.90	$47.90
Purchase #6	$62.41	3.462%	$64.5706	$64.57	$64.55	$64.60
Purchase #7	$221.63	11.302%	$246.6786	$246.68	$246.70	$246.70
7 purchase totals =	$891.54		$982.2492	$982.25	$982.25	$982.30