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	$196.52	12.181%	$220.4581	$220.46	$220.45	$220.50
Purchase #2	$234.29	7.403%	$251.6345	$251.63	$251.65	$251.60
Purchase #3	$107.54	10.148%	$118.4532	$118.45	$118.45	$118.50
Purchase #4	$63.56	6.224%	$67.516	$67.52	$67.50	$67.50
Purchase #5	$119.58	9.370%	$130.7846	$130.78	$130.80	$130.80
Purchase #6	$126.78	3.355%	$131.0335	$131.03	$131.05	$131.00
Purchase #7	$25.90	5.728%	$27.3836	$27.38	$27.40	$27.40
7 purchase totals =	$874.17		$947.2635	$947.25	$947.30	$947.30