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	$226.86	4.829%	$237.8151	$237.82	$237.80	$237.80
Purchase #2	$214.81	9.680%	$235.6036	$235.60	$235.60	$235.60
Purchase #3	$32.31	4.763%	$33.8489	$33.85	$33.85	$33.80
Purchase #4	$109.69	12.160%	$123.0283	$123.03	$123.05	$123.00
Purchase #5	$166.49	5.121%	$175.016	$175.02	$175.00	$175.00
Purchase #6	$149.52	10.672%	$165.4768	$165.48	$165.50	$165.50
Purchase #7	$69.71	4.320%	$72.7215	$72.72	$72.70	$72.70
7 purchase totals =	$969.39		$1,043.5102	$1,043.52	$1,043.50	$1,043.40