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	$11.59	4.544%	$12.1166	$12.12	$12.10	$12.10
Purchase #2	$217.70	12.114%	$244.0722	$244.07	$244.05	$244.10
Purchase #3	$79.29	7.612%	$85.3256	$85.33	$85.35	$85.30
Purchase #4	$98.28	8.324%	$106.4608	$106.46	$106.45	$106.50
Purchase #5	$84.67	11.561%	$94.4587	$94.46	$94.45	$94.50
Purchase #6	$38.80	6.542%	$41.3383	$41.34	$41.35	$41.30
Purchase #7	$107.77	3.616%	$111.667	$111.67	$111.65	$111.70
7 purchase totals =	$638.10		$695.4392	$695.45	$695.40	$695.50