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	$220.45	4.173%	$229.6494	$229.65	$229.65	$229.60
Purchase #2	$59.25	4.827%	$62.11	$62.11	$62.10	$62.10
Purchase #3	$9.68	4.438%	$10.1096	$10.11	$10.10	$10.10
Purchase #4	$144.29	8.495%	$156.5474	$156.55	$156.55	$156.50
Purchase #5	$248.29	6.339%	$264.0291	$264.03	$264.05	$264.00
Purchase #6	$147.42	13.198%	$166.8765	$166.88	$166.90	$166.90
Purchase #7	$231.90	12.443%	$260.7553	$260.76	$260.75	$260.80
7 purchase totals =	$1,061.28		$1,150.0773	$1,150.09	$1,150.10	$1,150.00