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	$192.57	10.316%	$212.4355	$212.44	$212.45	$212.40
Purchase #2	$143.73	12.545%	$161.7609	$161.76	$161.75	$161.80
Purchase #3	$45.30	10.857%	$50.2182	$50.22	$50.20	$50.20
Purchase #4	$157.94	11.325%	$175.8267	$175.83	$175.85	$175.80
Purchase #5	$10.64	5.171%	$11.1902	$11.19	$11.20	$11.20
Purchase #6	$81.54	11.485%	$90.9049	$90.90	$90.90	$90.90
Purchase #7	$136.89	10.675%	$151.503	$151.50	$151.50	$151.50
7 purchase totals =	$768.61		$853.8394	$853.84	$853.85	$853.80