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	$81.73	8.816%	$88.9353	$88.94	$88.95	$88.90
Purchase #2	$158.25	4.435%	$165.2684	$165.27	$165.25	$165.30
Purchase #3	$188.83	7.572%	$203.1282	$203.13	$203.15	$203.10
Purchase #4	$58.83	11.117%	$65.3701	$65.37	$65.35	$65.40
Purchase #5	$65.81	11.124%	$73.1307	$73.13	$73.15	$73.10
Purchase #6	$187.62	4.504%	$196.0704	$196.07	$196.05	$196.10
Purchase #7	$103.50	7.508%	$111.2708	$111.27	$111.25	$111.30
7 purchase totals =	$844.57		$903.1739	$903.18	$903.15	$903.20