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	$69.54	4.140%	$72.419	$72.42	$72.40	$72.40
Purchase #2	$84.53	11.522%	$94.2695	$94.27	$94.25	$94.30
Purchase #3	$240.67	8.185%	$260.3688	$260.37	$260.35	$260.40
Purchase #4	$77.77	12.314%	$87.3466	$87.35	$87.35	$87.30
Purchase #5	$179.56	3.355%	$185.5842	$185.58	$185.60	$185.60
Purchase #6	$157.27	8.191%	$170.152	$170.15	$170.15	$170.20
Purchase #7	$159.40	4.458%	$166.5061	$166.51	$166.50	$166.50
7 purchase totals =	$968.74		$1,036.6462	$1,036.65	$1,036.60	$1,036.70