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	$174.75	9.817%	$191.9052	$191.91	$191.90	$191.90
Purchase #2	$98.62	13.282%	$111.7187	$111.72	$111.70	$111.70
Purchase #3	$231.75	13.297%	$262.5658	$262.57	$262.55	$262.60
Purchase #4	$159.67	7.617%	$171.8321	$171.83	$171.85	$171.80
Purchase #5	$242.53	3.439%	$250.8706	$250.87	$250.85	$250.90
Purchase #6	$168.43	11.560%	$187.9005	$187.90	$187.90	$187.90
Purchase #7	$77.69	7.698%	$83.6706	$83.67	$83.65	$83.70
7 purchase totals =	$1,153.44		$1,260.4635	$1,260.47	$1,260.40	$1,260.50