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	$197.67	13.754%	$224.8575	$224.86	$224.85	$224.90
Purchase #2	$242.54	5.866%	$256.7674	$256.77	$256.75	$256.80
Purchase #3	$42.41	7.554%	$45.6137	$45.61	$45.60	$45.60
Purchase #4	$8.48	13.332%	$9.6106	$9.61	$9.60	$9.60
Purchase #5	$80.83	11.849%	$90.4075	$90.41	$90.40	$90.40
Purchase #6	$147.63	8.188%	$159.7179	$159.72	$159.70	$159.70
Purchase #7	$222.28	5.213%	$233.8675	$233.87	$233.85	$233.90
7 purchase totals =	$941.84		$1,020.8421	$1,020.85	$1,020.75	$1,020.90