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	$130.65	3.808%	$135.6252	$135.63	$135.65	$135.60
Purchase #2	$139.39	5.158%	$146.5797	$146.58	$146.60	$146.60
Purchase #3	$216.65	13.144%	$245.1265	$245.13	$245.15	$245.10
Purchase #4	$40.86	13.764%	$46.484	$46.48	$46.50	$46.50
Purchase #5	$175.60	6.784%	$187.5127	$187.51	$187.50	$187.50
Purchase #6	$111.78	13.799%	$127.2045	$127.20	$127.20	$127.20
Purchase #7	$146.38	6.364%	$155.6956	$155.70	$155.70	$155.70
7 purchase totals =	$961.31		$1,044.2282	$1,044.23	$1,044.30	$1,044.20