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	$221.38	11.352%	$246.5111	$246.51	$246.50	$246.50
Purchase #2	$147.94	11.674%	$165.2105	$165.21	$165.20	$165.20
Purchase #3	$229.63	11.779%	$256.6781	$256.68	$256.70	$256.70
Purchase #4	$52.29	4.466%	$54.6253	$54.63	$54.65	$54.60
Purchase #5	$174.39	9.374%	$190.7373	$190.74	$190.75	$190.70
Purchase #6	$40.44	11.406%	$45.0526	$45.05	$45.05	$45.10
Purchase #7	$126.91	6.175%	$134.7467	$134.75	$134.75	$134.70
7 purchase totals =	$992.98		$1,093.5616	$1,093.57	$1,093.60	$1,093.50