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	$175.66	5.332%	$185.0262	$185.03	$185.05	$185.00
Purchase #2	$208.38	6.782%	$222.5123	$222.51	$222.50	$222.50
Purchase #3	$20.61	12.161%	$23.1164	$23.12	$23.10	$23.10
Purchase #4	$133.34	13.624%	$151.5062	$151.51	$151.50	$151.50
Purchase #5	$108.48	9.648%	$118.9462	$118.95	$118.95	$118.90
Purchase #6	$180.61	4.843%	$189.3569	$189.36	$189.35	$189.40
Purchase #7	$54.25	13.823%	$61.749	$61.75	$61.75	$61.70
7 purchase totals =	$881.33		$952.2132	$952.23	$952.20	$952.10