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	$123.76	11.371%	$137.8327	$137.83	$137.85	$137.80
Purchase #2	$10.63	8.465%	$11.5298	$11.53	$11.55	$11.50
Purchase #3	$62.90	13.270%	$71.2468	$71.25	$71.25	$71.20
Purchase #4	$114.54	8.249%	$123.9884	$123.99	$124.00	$124.00
Purchase #5	$120.38	8.367%	$130.4522	$130.45	$130.45	$130.50
Purchase #6	$156.93	9.786%	$172.2872	$172.29	$172.30	$172.30
Purchase #7	$236.67	8.500%	$256.787	$256.79	$256.80	$256.80
7 purchase totals =	$825.81		$904.1241	$904.13	$904.20	$904.10