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	$46.71	8.792%	$50.8167	$50.82	$50.80	$50.80
Purchase #2	$133.58	12.764%	$150.6302	$150.63	$150.65	$150.60
Purchase #3	$62.79	6.538%	$66.8952	$66.90	$66.90	$66.90
Purchase #4	$215.37	4.541%	$225.15	$225.15	$225.15	$225.20
Purchase #5	$233.29	10.852%	$258.6066	$258.61	$258.60	$258.60
Purchase #6	$215.70	13.371%	$244.5412	$244.54	$244.55	$244.50
Purchase #7	$178.49	11.148%	$198.3881	$198.39	$198.40	$198.40
7 purchase totals =	$1,085.93		$1,195.0280	$1,195.04	$1,195.05	$1,195.00