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	$151.29	11.773%	$169.1014	$169.10	$169.10	$169.10
Purchase #2	$18.35	11.490%	$20.4584	$20.46	$20.45	$20.50
Purchase #3	$19.58	11.404%	$21.8129	$21.81	$21.80	$21.80
Purchase #4	$43.67	6.211%	$46.3823	$46.38	$46.40	$46.40
Purchase #5	$189.82	9.666%	$208.168	$208.17	$208.15	$208.20
Purchase #6	$195.38	11.181%	$217.2254	$217.23	$217.25	$217.20
Purchase #7	$178.45	13.770%	$203.0226	$203.02	$203.00	$203.00
7 purchase totals =	$796.54		$886.1710	$886.17	$886.15	$886.20