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	$231.48	7.447%	$248.7183	$248.72	$248.70	$248.70
Purchase #2	$69.27	13.489%	$78.6138	$78.61	$78.60	$78.60
Purchase #3	$57.71	6.313%	$61.3532	$61.35	$61.35	$61.40
Purchase #4	$60.45	6.740%	$64.5243	$64.52	$64.50	$64.50
Purchase #5	$224.89	3.456%	$232.6622	$232.66	$232.65	$232.70
Purchase #6	$124.99	4.500%	$130.6146	$130.61	$130.60	$130.60
Purchase #7	$114.31	11.109%	$127.0087	$127.01	$127.00	$127.00
7 purchase totals =	$883.10		$943.4951	$943.48	$943.40	$943.50