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	$152.33	13.501%	$172.8961	$172.90	$172.90	$172.90
Purchase #2	$41.44	13.792%	$47.1554	$47.16	$47.15	$47.20
Purchase #3	$150.29	7.575%	$161.6745	$161.67	$161.65	$161.70
Purchase #4	$94.46	5.264%	$99.4324	$99.43	$99.45	$99.40
Purchase #5	$218.88	9.125%	$238.8528	$238.85	$238.85	$238.90
Purchase #6	$98.53	11.817%	$110.1733	$110.17	$110.15	$110.20
Purchase #7	$135.28	11.675%	$151.0739	$151.07	$151.05	$151.10
7 purchase totals =	$891.21		$981.2584	$981.25	$981.20	$981.40