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	$232.77	11.531%	$259.6107	$259.61	$259.60	$259.60
Purchase #2	$211.97	6.380%	$225.4937	$225.49	$225.50	$225.50
Purchase #3	$187.68	4.733%	$196.5629	$196.56	$196.55	$196.60
Purchase #4	$216.44	5.504%	$228.3529	$228.35	$228.35	$228.40
Purchase #5	$212.87	4.579%	$222.6173	$222.62	$222.60	$222.60
Purchase #6	$57.71	3.550%	$59.7587	$59.76	$59.75	$59.80
Purchase #7	$88.60	6.602%	$94.4494	$94.45	$94.45	$94.40
7 purchase totals =	$1,208.04		$1,286.8456	$1,286.84	$1,286.80	$1,286.90