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	$146.88	12.715%	$165.5558	$165.56	$165.55	$165.60
Purchase #2	$64.48	10.482%	$71.2388	$71.24	$71.25	$71.20
Purchase #3	$160.44	7.573%	$172.5901	$172.59	$172.60	$172.60
Purchase #4	$136.67	8.449%	$148.2172	$148.22	$148.20	$148.20
Purchase #5	$202.56	3.866%	$210.391	$210.39	$210.40	$210.40
Purchase #6	$143.34	10.397%	$158.2431	$158.24	$158.25	$158.20
Purchase #7	$145.49	4.341%	$151.8057	$151.81	$151.80	$151.80
7 purchase totals =	$999.86		$1,078.0417	$1,078.05	$1,078.05	$1,078.00