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	$185.56	7.871%	$200.1654	$200.17	$200.15	$200.20
Purchase #2	$88.67	13.123%	$100.3062	$100.31	$100.30	$100.30
Purchase #3	$203.70	10.389%	$224.8624	$224.86	$224.85	$224.90
Purchase #4	$213.65	3.810%	$221.7901	$221.79	$221.80	$221.80
Purchase #5	$31.52	8.864%	$34.3139	$34.31	$34.30	$34.30
Purchase #6	$248.26	11.352%	$276.4425	$276.44	$276.45	$276.40
Purchase #7	$154.54	12.280%	$173.5175	$173.52	$173.50	$173.50
7 purchase totals =	$1,125.90		$1,231.3980	$1,231.40	$1,231.35	$1,231.40