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	$208.71	10.275%	$230.155	$230.16	$230.15	$230.20
Purchase #2	$92.73	8.737%	$100.8318	$100.83	$100.85	$100.80
Purchase #3	$84.67	12.614%	$95.3503	$95.35	$95.35	$95.40
Purchase #4	$38.53	13.219%	$43.6233	$43.62	$43.60	$43.60
Purchase #5	$92.35	7.505%	$99.2809	$99.28	$99.30	$99.30
Purchase #6	$245.86	7.388%	$264.0241	$264.02	$264.00	$264.00
Purchase #7	$143.74	13.601%	$163.2901	$163.29	$163.30	$163.30
7 purchase totals =	$906.59		$996.5555	$996.55	$996.55	$996.60