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	$178.42	12.406%	$200.5548	$200.55	$200.55	$200.60
Purchase #2	$246.82	11.603%	$275.4585	$275.46	$275.45	$275.50
Purchase #3	$153.44	5.274%	$161.5324	$161.53	$161.55	$161.50
Purchase #4	$133.49	11.308%	$148.585	$148.59	$148.60	$148.60
Purchase #5	$77.31	7.350%	$82.9923	$82.99	$83.00	$83.00
Purchase #6	$7.84	8.291%	$8.49	$8.49	$8.50	$8.50
Purchase #7	$117.51	7.172%	$125.9378	$125.94	$125.95	$125.90
7 purchase totals =	$914.83		$1,003.5508	$1,003.55	$1,003.60	$1,003.60