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	$131.72	4.439%	$137.5671	$137.57	$137.55	$137.60
Purchase #2	$164.42	11.389%	$183.1458	$183.15	$183.15	$183.10
Purchase #3	$139.88	7.551%	$150.4423	$150.44	$150.45	$150.40
Purchase #4	$233.85	8.394%	$253.4794	$253.48	$253.50	$253.50
Purchase #5	$161.37	7.578%	$173.5986	$173.60	$173.60	$173.60
Purchase #6	$121.32	12.538%	$136.5311	$136.53	$136.55	$136.50
Purchase #7	$219.80	9.578%	$240.8524	$240.85	$240.85	$240.90
7 purchase totals =	$1,172.36		$1,275.6167	$1,275.62	$1,275.65	$1,275.60