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	$146.73	6.605%	$156.4215	$156.42	$156.40	$156.40
Purchase #2	$157.78	10.245%	$173.9446	$173.94	$173.95	$173.90
Purchase #3	$71.71	13.561%	$81.4346	$81.43	$81.45	$81.40
Purchase #4	$100.91	4.574%	$105.5256	$105.53	$105.55	$105.50
Purchase #5	$142.66	10.689%	$157.9089	$157.91	$157.90	$157.90
Purchase #6	$67.78	5.430%	$71.4605	$71.46	$71.45	$71.50
Purchase #7	$44.26	9.809%	$48.6015	$48.60	$48.60	$48.60
7 purchase totals =	$731.83		$795.2972	$795.29	$795.30	$795.20