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	$231.83	13.637%	$263.4447	$263.44	$263.45	$263.40
Purchase #2	$141.73	7.628%	$152.5412	$152.54	$152.55	$152.50
Purchase #3	$159.47	8.205%	$172.5545	$172.55	$172.55	$172.60
Purchase #4	$42.60	12.630%	$47.9804	$47.98	$48.00	$48.00
Purchase #5	$89.61	13.622%	$101.8167	$101.82	$101.80	$101.80
Purchase #6	$129.40	11.593%	$144.4013	$144.40	$144.40	$144.40
Purchase #7	$137.90	12.223%	$154.7555	$154.76	$154.75	$154.80
7 purchase totals =	$932.54		$1,037.4943	$1,037.49	$1,037.50	$1,037.50