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	$188.45	5.177%	$198.2061	$198.21	$198.20	$198.20
Purchase #2	$160.77	9.568%	$176.1525	$176.15	$176.15	$176.20
Purchase #3	$56.77	4.503%	$59.3264	$59.33	$59.35	$59.30
Purchase #4	$188.73	10.555%	$208.6505	$208.65	$208.65	$208.70
Purchase #5	$244.75	10.136%	$269.5579	$269.56	$269.55	$269.60
Purchase #6	$124.72	4.452%	$130.2725	$130.27	$130.25	$130.30
Purchase #7	$243.82	12.730%	$274.8583	$274.86	$274.85	$274.90
7 purchase totals =	$1,208.01		$1,317.0242	$1,317.03	$1,317.00	$1,317.20