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	$242.79	13.518%	$275.6104	$275.61	$275.60	$275.60
Purchase #2	$222.98	4.776%	$233.6295	$233.63	$233.65	$233.60
Purchase #3	$42.89	8.693%	$46.6184	$46.62	$46.60	$46.60
Purchase #4	$63.75	6.457%	$67.8663	$67.87	$67.85	$67.90
Purchase #5	$187.85	7.436%	$201.8185	$201.82	$201.80	$201.80
Purchase #6	$174.42	13.132%	$197.3248	$197.32	$197.30	$197.30
Purchase #7	$192.42	3.619%	$199.3837	$199.38	$199.40	$199.40
7 purchase totals =	$1,127.10		$1,222.2516	$1,222.25	$1,222.20	$1,222.20