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	$210.59	8.700%	$228.9113	$228.91	$228.90	$228.90
Purchase #2	$219.33	7.315%	$235.374	$235.37	$235.35	$235.40
Purchase #3	$37.63	10.163%	$41.4543	$41.45	$41.45	$41.50
Purchase #4	$126.70	10.537%	$140.0504	$140.05	$140.05	$140.10
Purchase #5	$158.41	10.474%	$175.0019	$175.00	$175.00	$175.00
Purchase #6	$33.68	10.190%	$37.112	$37.11	$37.10	$37.10
Purchase #7	$247.48	7.282%	$265.5015	$265.50	$265.50	$265.50
7 purchase totals =	$1,033.82		$1,123.4054	$1,123.39	$1,123.35	$1,123.50