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	$199.96	10.794%	$221.5437	$221.54	$221.55	$221.50
Purchase #2	$34.59	6.347%	$36.7854	$36.79	$36.80	$36.80
Purchase #3	$235.44	12.778%	$265.5245	$265.52	$265.50	$265.50
Purchase #4	$68.82	3.860%	$71.4765	$71.48	$71.50	$71.50
Purchase #5	$68.58	4.759%	$71.8437	$71.84	$71.85	$71.80
Purchase #6	$83.71	6.686%	$89.3069	$89.31	$89.30	$89.30
Purchase #7	$247.65	12.778%	$279.2947	$279.29	$279.30	$279.30
7 purchase totals =	$938.75		$1,035.7754	$1,035.77	$1,035.80	$1,035.70