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	$54.83	9.119%	$59.8299	$59.83	$59.85	$59.80
Purchase #2	$106.80	13.428%	$121.1411	$121.14	$121.15	$121.10
Purchase #3	$124.81	12.764%	$140.7407	$140.74	$140.75	$140.70
Purchase #4	$209.85	13.413%	$237.9972	$238.00	$238.00	$238.00
Purchase #5	$173.77	11.518%	$193.7848	$193.78	$193.80	$193.80
Purchase #6	$100.34	11.229%	$111.6072	$111.61	$111.60	$111.60
Purchase #7	$226.83	12.371%	$254.8911	$254.89	$254.90	$254.90
7 purchase totals =	$997.23		$1,119.9920	$1,119.99	$1,120.05	$1,119.90