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	$213.94	6.219%	$227.2449	$227.24	$227.25	$227.20
Purchase #2	$87.65	8.648%	$95.23	$95.23	$95.25	$95.20
Purchase #3	$119.67	6.483%	$127.4282	$127.43	$127.45	$127.40
Purchase #4	$127.42	8.215%	$137.8876	$137.89	$137.90	$137.90
Purchase #5	$249.66	10.312%	$275.4049	$275.40	$275.40	$275.40
Purchase #6	$14.81	7.631%	$15.9402	$15.94	$15.95	$15.90
Purchase #7	$185.36	9.362%	$202.7134	$202.71	$202.70	$202.70
7 purchase totals =	$998.51		$1,081.8492	$1,081.84	$1,081.90	$1,081.70