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	$68.26	5.198%	$71.8082	$71.81	$71.80	$71.80
Purchase #2	$36.59	3.514%	$37.8758	$37.88	$37.90	$37.90
Purchase #3	$36.37	9.651%	$39.8801	$39.88	$39.90	$39.90
Purchase #4	$65.91	11.209%	$73.2979	$73.30	$73.30	$73.30
Purchase #5	$248.71	13.221%	$281.5919	$281.59	$281.60	$281.60
Purchase #6	$71.91	13.326%	$81.4927	$81.49	$81.50	$81.50
Purchase #7	$140.29	7.210%	$150.4049	$150.40	$150.40	$150.40
7 purchase totals =	$668.04		$736.3515	$736.35	$736.40	$736.40