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	$143.25	3.671%	$148.5087	$148.51	$148.50	$148.50
Purchase #2	$35.34	7.672%	$38.0513	$38.05	$38.05	$38.10
Purchase #3	$191.48	10.728%	$212.022	$212.02	$212.00	$212.00
Purchase #4	$213.55	11.864%	$238.8856	$238.89	$238.90	$238.90
Purchase #5	$234.51	3.128%	$241.8455	$241.85	$241.85	$241.80
Purchase #6	$198.58	13.510%	$225.4082	$225.41	$225.40	$225.40
Purchase #7	$44.42	4.586%	$46.4571	$46.46	$46.45	$46.50
7 purchase totals =	$1,061.13		$1,151.1784	$1,151.19	$1,151.15	$1,151.20