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	$169.61	10.144%	$186.8152	$186.82	$186.80	$186.80
Purchase #2	$158.79	7.315%	$170.4055	$170.41	$170.40	$170.40
Purchase #3	$71.47	10.188%	$78.7514	$78.75	$78.75	$78.80
Purchase #4	$125.43	9.771%	$137.6858	$137.69	$137.70	$137.70
Purchase #5	$229.50	6.530%	$244.4864	$244.49	$244.50	$244.50
Purchase #6	$55.25	9.541%	$60.5214	$60.52	$60.50	$60.50
Purchase #7	$59.72	4.157%	$62.2026	$62.20	$62.20	$62.20
7 purchase totals =	$869.77		$940.8683	$940.88	$940.85	$940.90