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	$144.63	4.324%	$150.8838	$150.88	$150.90	$150.90
Purchase #2	$141.60	5.567%	$149.4829	$149.48	$149.50	$149.50
Purchase #3	$115.47	11.781%	$129.0735	$129.07	$129.05	$129.10
Purchase #4	$195.37	13.560%	$221.8622	$221.86	$221.85	$221.90
Purchase #5	$173.42	4.485%	$181.1979	$181.20	$181.20	$181.20
Purchase #6	$111.66	10.802%	$123.7215	$123.72	$123.70	$123.70
Purchase #7	$79.60	13.301%	$90.1876	$90.19	$90.20	$90.20
7 purchase totals =	$961.75		$1,046.4094	$1,046.40	$1,046.40	$1,046.50