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	$67.43	4.529%	$70.4839	$70.48	$70.50	$70.50
Purchase #2	$47.38	5.313%	$49.8973	$49.90	$49.90	$49.90
Purchase #3	$174.35	7.439%	$187.3199	$187.32	$187.30	$187.30
Purchase #4	$246.47	3.707%	$255.6066	$255.61	$255.60	$255.60
Purchase #5	$100.88	11.144%	$112.1221	$112.12	$112.10	$112.10
Purchase #6	$230.89	11.148%	$256.6296	$256.63	$256.65	$256.60
Purchase #7	$192.63	8.752%	$209.489	$209.49	$209.50	$209.50
7 purchase totals =	$1,060.03		$1,141.5484	$1,141.55	$1,141.55	$1,141.50