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	$231.78	9.387%	$253.5372	$253.54	$253.55	$253.50
Purchase #2	$229.36	8.457%	$248.757	$248.76	$248.75	$248.80
Purchase #3	$55.73	6.212%	$59.1919	$59.19	$59.20	$59.20
Purchase #4	$78.81	11.806%	$88.1143	$88.11	$88.10	$88.10
Purchase #5	$182.71	4.853%	$191.5769	$191.58	$191.60	$191.60
Purchase #6	$37.41	13.534%	$42.4731	$42.47	$42.45	$42.50
Purchase #7	$146.59	10.848%	$162.4921	$162.49	$162.50	$162.50
7 purchase totals =	$962.39		$1,046.1425	$1,046.14	$1,046.15	$1,046.20