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	$101.36	11.510%	$113.0265	$113.03	$113.05	$113.00
Purchase #2	$34.95	8.288%	$37.8467	$37.85	$37.85	$37.80
Purchase #3	$70.31	3.493%	$72.7659	$72.77	$72.75	$72.80
Purchase #4	$175.60	8.587%	$190.6788	$190.68	$190.70	$190.70
Purchase #5	$47.65	6.819%	$50.8993	$50.90	$50.90	$50.90
Purchase #6	$22.28	10.187%	$24.5497	$24.55	$24.55	$24.50
Purchase #7	$75.47	3.593%	$78.1816	$78.18	$78.20	$78.20
7 purchase totals =	$527.62		$567.9485	$567.96	$568.00	$567.90