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	$191.54	4.342%	$199.8567	$199.86	$199.85	$199.90
Purchase #2	$110.90	13.492%	$125.8626	$125.86	$125.85	$125.90
Purchase #3	$33.58	8.808%	$36.5377	$36.54	$36.55	$36.50
Purchase #4	$153.49	12.677%	$172.9479	$172.95	$172.95	$172.90
Purchase #5	$189.36	12.186%	$212.4354	$212.44	$212.45	$212.40
Purchase #6	$12.43	6.829%	$13.2788	$13.28	$13.30	$13.30
Purchase #7	$29.38	10.496%	$32.4637	$32.46	$32.45	$32.50
7 purchase totals =	$720.68		$793.3828	$793.39	$793.40	$793.40