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	$85.88	11.207%	$95.5046	$95.50	$95.50	$95.50
Purchase #2	$66.95	7.676%	$72.0891	$72.09	$72.10	$72.10
Purchase #3	$121.89	7.594%	$131.1463	$131.15	$131.15	$131.10
Purchase #4	$56.34	4.810%	$59.05	$59.05	$59.05	$59.10
Purchase #5	$175.76	10.485%	$194.1884	$194.19	$194.20	$194.20
Purchase #6	$69.60	13.359%	$78.8979	$78.90	$78.90	$78.90
Purchase #7	$47.85	6.456%	$50.9392	$50.94	$50.95	$50.90
7 purchase totals =	$624.27		$681.8155	$681.82	$681.85	$681.80