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	$153.94	11.775%	$172.0664	$172.07	$172.05	$172.10
Purchase #2	$66.40	12.374%	$74.6163	$74.62	$74.60	$74.60
Purchase #3	$155.39	11.148%	$172.7129	$172.71	$172.70	$172.70
Purchase #4	$105.49	12.695%	$118.882	$118.88	$118.90	$118.90
Purchase #5	$232.47	12.715%	$262.0286	$262.03	$262.05	$262.00
Purchase #6	$192.37	4.228%	$200.5034	$200.50	$200.50	$200.50
Purchase #7	$17.80	6.313%	$18.9237	$18.92	$18.90	$18.90
7 purchase totals =	$923.86		$1,019.7333	$1,019.73	$1,019.70	$1,019.70