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	$246.50	6.471%	$262.451	$262.45	$262.45	$262.50
Purchase #2	$115.83	13.456%	$131.4161	$131.42	$131.40	$131.40
Purchase #3	$227.63	10.610%	$251.7815	$251.78	$251.80	$251.80
Purchase #4	$197.77	12.463%	$222.4181	$222.42	$222.40	$222.40
Purchase #5	$234.36	10.693%	$259.4201	$259.42	$259.40	$259.40
Purchase #6	$130.84	8.249%	$141.633	$141.63	$141.65	$141.60
Purchase #7	$175.58	5.828%	$185.8128	$185.81	$185.80	$185.80
7 purchase totals =	$1,328.51		$1,454.9326	$1,454.93	$1,454.90	$1,454.90