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	$235.72	7.453%	$253.2882	$253.29	$253.30	$253.30
Purchase #2	$147.31	12.181%	$165.2538	$165.25	$165.25	$165.30
Purchase #3	$209.37	12.123%	$234.7519	$234.75	$234.75	$234.80
Purchase #4	$189.71	13.219%	$214.7878	$214.79	$214.80	$214.80
Purchase #5	$209.69	7.450%	$225.3119	$225.31	$225.30	$225.30
Purchase #6	$129.32	9.405%	$141.4825	$141.48	$141.50	$141.50
Purchase #7	$116.62	9.710%	$127.9438	$127.94	$127.95	$127.90
7 purchase totals =	$1,237.74		$1,362.8199	$1,362.81	$1,362.85	$1,362.90