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	$44.43	3.834%	$46.1334	$46.13	$46.15	$46.10
Purchase #2	$243.47	13.374%	$276.0317	$276.03	$276.05	$276.00
Purchase #3	$100.39	3.117%	$103.5192	$103.52	$103.50	$103.50
Purchase #4	$47.83	13.585%	$54.3277	$54.33	$54.35	$54.30
Purchase #5	$196.68	12.675%	$221.6092	$221.61	$221.60	$221.60
Purchase #6	$30.30	13.537%	$34.4017	$34.40	$34.40	$34.40
Purchase #7	$28.29	13.249%	$32.0381	$32.04	$32.05	$32.00
7 purchase totals =	$691.39		$768.0610	$768.06	$768.10	$767.90