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	$105.60	7.425%	$113.4408	$113.44	$113.45	$113.40
Purchase #2	$122.58	11.614%	$136.8164	$136.82	$136.80	$136.80
Purchase #3	$247.60	9.124%	$270.191	$270.19	$270.20	$270.20
Purchase #4	$136.53	7.309%	$146.509	$146.51	$146.50	$146.50
Purchase #5	$11.55	3.172%	$11.9164	$11.92	$11.90	$11.90
Purchase #6	$94.86	10.738%	$105.0461	$105.05	$105.05	$105.00
Purchase #7	$139.43	5.227%	$146.718	$146.72	$146.70	$146.70
7 purchase totals =	$858.15		$930.6377	$930.65	$930.60	$930.50