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	$84.78	12.668%	$95.5199	$95.52	$95.50	$95.50
Purchase #2	$168.76	12.175%	$189.3065	$189.31	$189.30	$189.30
Purchase #3	$12.90	7.663%	$13.8885	$13.89	$13.90	$13.90
Purchase #4	$93.76	10.552%	$103.6536	$103.65	$103.65	$103.70
Purchase #5	$94.47	7.422%	$101.4816	$101.48	$101.50	$101.50
Purchase #6	$222.45	4.514%	$232.4914	$232.49	$232.50	$232.50
Purchase #7	$61.48	10.809%	$68.1254	$68.13	$68.15	$68.10
7 purchase totals =	$738.60		$804.4669	$804.47	$804.50	$804.50