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	$187.36	3.643%	$194.1855	$194.19	$194.20	$194.20
Purchase #2	$187.55	11.208%	$208.5706	$208.57	$208.55	$208.60
Purchase #3	$83.65	7.403%	$89.8426	$89.84	$89.85	$89.80
Purchase #4	$22.42	11.228%	$24.9373	$24.94	$24.95	$24.90
Purchase #5	$37.55	9.289%	$41.038	$41.04	$41.05	$41.00
Purchase #6	$57.47	7.771%	$61.936	$61.94	$61.95	$61.90
Purchase #7	$65.67	10.718%	$72.7085	$72.71	$72.70	$72.70
7 purchase totals =	$641.67		$693.2185	$693.23	$693.25	$693.10