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	$61.42	4.636%	$64.2674	$64.27	$64.25	$64.30
Purchase #2	$148.98	5.792%	$157.6089	$157.61	$157.60	$157.60
Purchase #3	$147.75	5.533%	$155.925	$155.93	$155.95	$155.90
Purchase #4	$123.53	7.324%	$132.5773	$132.58	$132.60	$132.60
Purchase #5	$23.71	9.199%	$25.8911	$25.89	$25.90	$25.90
Purchase #6	$37.35	9.800%	$41.0103	$41.01	$41.00	$41.00
Purchase #7	$207.59	7.866%	$223.919	$223.92	$223.90	$223.90
7 purchase totals =	$750.33		$801.1990	$801.21	$801.20	$801.20