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	$132.30	12.477%	$148.8071	$148.81	$148.80	$148.80
Purchase #2	$137.82	12.701%	$155.3245	$155.32	$155.30	$155.30
Purchase #3	$53.31	12.213%	$59.8208	$59.82	$59.80	$59.80
Purchase #4	$249.61	6.721%	$266.3863	$266.39	$266.40	$266.40
Purchase #5	$221.46	11.182%	$246.2237	$246.22	$246.20	$246.20
Purchase #6	$85.44	8.293%	$92.5255	$92.53	$92.55	$92.50
Purchase #7	$173.29	9.685%	$190.0731	$190.07	$190.05	$190.10
7 purchase totals =	$1,053.23		$1,159.1610	$1,159.16	$1,159.10	$1,159.10