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	$201.46	13.767%	$229.195	$229.20	$229.20	$229.20
Purchase #2	$49.76	9.319%	$54.3971	$54.40	$54.40	$54.40
Purchase #3	$80.39	12.345%	$90.3141	$90.31	$90.30	$90.30
Purchase #4	$55.66	6.200%	$59.1109	$59.11	$59.10	$59.10
Purchase #5	$181.76	6.315%	$193.2381	$193.24	$193.25	$193.20
Purchase #6	$137.89	6.556%	$146.9301	$146.93	$146.95	$146.90
Purchase #7	$151.54	9.223%	$165.5165	$165.52	$165.50	$165.50
7 purchase totals =	$858.46		$938.7018	$938.71	$938.70	$938.60