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	$103.42	12.328%	$116.1696	$116.17	$116.15	$116.20
Purchase #2	$157.48	9.181%	$171.9382	$171.94	$171.95	$171.90
Purchase #3	$173.72	6.794%	$185.5225	$185.52	$185.50	$185.50
Purchase #4	$224.36	13.311%	$254.2246	$254.22	$254.20	$254.20
Purchase #5	$172.45	10.751%	$190.9901	$190.99	$191.00	$191.00
Purchase #6	$166.85	9.297%	$182.362	$182.36	$182.35	$182.40
Purchase #7	$63.57	5.791%	$67.2513	$67.25	$67.25	$67.30
7 purchase totals =	$1,061.85		$1,168.4583	$1,168.45	$1,168.40	$1,168.50