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	$134.83	10.738%	$149.308	$149.31	$149.30	$149.30
Purchase #2	$64.35	12.386%	$72.3204	$72.32	$72.30	$72.30
Purchase #3	$71.77	11.691%	$80.1606	$80.16	$80.15	$80.20
Purchase #4	$99.69	4.470%	$104.1461	$104.15	$104.15	$104.10
Purchase #5	$142.74	7.214%	$153.0373	$153.04	$153.05	$153.00
Purchase #6	$28.87	13.348%	$32.7236	$32.72	$32.70	$32.70
Purchase #7	$136.50	3.668%	$141.5068	$141.51	$141.50	$141.50
7 purchase totals =	$678.75		$733.2028	$733.21	$733.15	$733.10