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	$124.67	13.162%	$141.0791	$141.08	$141.10	$141.10
Purchase #2	$181.51	13.434%	$205.8941	$205.89	$205.90	$205.90
Purchase #3	$39.87	12.120%	$44.7022	$44.70	$44.70	$44.70
Purchase #4	$152.39	12.520%	$171.4692	$171.47	$171.45	$171.50
Purchase #5	$192.51	10.814%	$213.328	$213.33	$213.35	$213.30
Purchase #6	$200.25	3.485%	$207.2287	$207.23	$207.25	$207.20
Purchase #7	$97.87	13.511%	$111.0932	$111.09	$111.10	$111.10
7 purchase totals =	$989.07		$1,094.7945	$1,094.79	$1,094.85	$1,094.80