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	$42.30	7.153%	$45.3257	$45.33	$45.35	$45.30
Purchase #2	$113.88	3.863%	$118.2792	$118.28	$118.30	$118.30
Purchase #3	$12.90	12.363%	$14.4948	$14.49	$14.50	$14.50
Purchase #4	$155.96	10.562%	$172.4325	$172.43	$172.45	$172.40
Purchase #5	$50.95	12.473%	$57.305	$57.31	$57.30	$57.30
Purchase #6	$221.76	10.639%	$245.353	$245.35	$245.35	$245.40
Purchase #7	$81.73	12.443%	$91.8997	$91.90	$91.90	$91.90
7 purchase totals =	$679.48		$745.0899	$745.09	$745.15	$745.10