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	$178.48	6.536%	$190.1455	$190.15	$190.15	$190.10
Purchase #2	$201.33	13.778%	$229.0692	$229.07	$229.05	$229.10
Purchase #3	$195.41	10.625%	$216.1723	$216.17	$216.15	$216.20
Purchase #4	$91.40	11.152%	$101.5929	$101.59	$101.60	$101.60
Purchase #5	$58.75	8.232%	$63.5863	$63.59	$63.60	$63.60
Purchase #6	$154.89	11.663%	$172.9548	$172.95	$172.95	$173.00
Purchase #7	$111.78	7.196%	$119.8237	$119.82	$119.80	$119.80
7 purchase totals =	$992.04		$1,093.3447	$1,093.34	$1,093.30	$1,093.40