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	$129.93	12.793%	$146.5519	$146.55	$146.55	$146.60
Purchase #2	$202.86	6.681%	$216.4131	$216.41	$216.40	$216.40
Purchase #3	$196.51	11.388%	$218.8886	$218.89	$218.90	$218.90
Purchase #4	$152.77	7.643%	$164.4462	$164.45	$164.45	$164.40
Purchase #5	$234.62	8.749%	$255.1469	$255.15	$255.15	$255.10
Purchase #6	$197.60	5.460%	$208.389	$208.39	$208.40	$208.40
Purchase #7	$138.55	13.259%	$156.9203	$156.92	$156.90	$156.90
7 purchase totals =	$1,252.84		$1,366.7560	$1,366.76	$1,366.75	$1,366.70