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	$179.44	11.210%	$199.5552	$199.56	$199.55	$199.60
Purchase #2	$59.57	13.631%	$67.69	$67.69	$67.70	$67.70
Purchase #3	$100.87	4.798%	$105.7097	$105.71	$105.70	$105.70
Purchase #4	$103.25	6.607%	$110.0717	$110.07	$110.05	$110.10
Purchase #5	$43.27	5.735%	$45.7515	$45.75	$45.75	$45.80
Purchase #6	$32.64	3.476%	$33.7746	$33.77	$33.75	$33.80
Purchase #7	$102.37	9.143%	$111.7297	$111.73	$111.75	$111.70
7 purchase totals =	$621.41		$674.2824	$674.28	$674.25	$674.40