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	$43.92	4.706%	$45.9869	$45.99	$46.00	$46.00
Purchase #2	$77.93	9.552%	$85.3739	$85.37	$85.35	$85.40
Purchase #3	$81.88	9.301%	$89.4957	$89.50	$89.50	$89.50
Purchase #4	$131.67	8.491%	$142.8501	$142.85	$142.85	$142.90
Purchase #5	$120.35	3.706%	$124.8102	$124.81	$124.80	$124.80
Purchase #6	$25.56	9.738%	$28.049	$28.05	$28.05	$28.00
Purchase #7	$200.70	10.735%	$222.2451	$222.25	$222.25	$222.20
7 purchase totals =	$682.01		$738.8109	$738.82	$738.80	$738.80