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	$214.99	13.381%	$243.7578	$243.76	$243.75	$243.80
Purchase #2	$24.57	3.459%	$25.4199	$25.42	$25.40	$25.40
Purchase #3	$86.67	3.838%	$89.9964	$90.00	$90.00	$90.00
Purchase #4	$160.78	4.178%	$167.4974	$167.50	$167.50	$167.50
Purchase #5	$172.47	11.843%	$192.8956	$192.90	$192.90	$192.90
Purchase #6	$155.73	11.181%	$173.1422	$173.14	$173.15	$173.10
Purchase #7	$61.50	11.243%	$68.4144	$68.41	$68.40	$68.40
7 purchase totals =	$876.71		$961.1237	$961.13	$961.10	$961.10