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	$211.43	9.423%	$231.353	$231.35	$231.35	$231.40
Purchase #2	$248.51	5.693%	$262.6577	$262.66	$262.65	$262.70
Purchase #3	$198.26	11.732%	$221.5199	$221.52	$221.50	$221.50
Purchase #4	$175.33	8.692%	$190.5697	$190.57	$190.55	$190.60
Purchase #5	$192.73	12.547%	$216.9118	$216.91	$216.90	$216.90
Purchase #6	$184.52	8.519%	$200.2393	$200.24	$200.25	$200.20
Purchase #7	$81.57	9.610%	$89.4089	$89.41	$89.40	$89.40
7 purchase totals =	$1,292.35		$1,412.6603	$1,412.66	$1,412.60	$1,412.70