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	$231.75	13.725%	$263.5577	$263.56	$263.55	$263.60
Purchase #2	$238.96	7.208%	$256.1842	$256.18	$256.20	$256.20
Purchase #3	$61.45	8.566%	$66.7138	$66.71	$66.70	$66.70
Purchase #4	$151.55	11.121%	$168.4039	$168.40	$168.40	$168.40
Purchase #5	$207.91	4.119%	$216.4738	$216.47	$216.45	$216.50
Purchase #6	$140.88	4.443%	$147.1393	$147.14	$147.15	$147.10
Purchase #7	$21.40	11.288%	$23.8156	$23.82	$23.80	$23.80
7 purchase totals =	$1,053.90		$1,142.2883	$1,142.28	$1,142.25	$1,142.30