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	$193.71	11.830%	$216.6259	$216.63	$216.65	$216.60
Purchase #2	$215.99	10.580%	$238.8417	$238.84	$238.85	$238.80
Purchase #3	$172.34	10.766%	$190.8941	$190.89	$190.90	$190.90
Purchase #4	$135.41	13.457%	$153.6321	$153.63	$153.65	$153.60
Purchase #5	$171.83	8.490%	$186.4184	$186.42	$186.40	$186.40
Purchase #6	$80.56	6.546%	$85.8335	$85.83	$85.85	$85.80
Purchase #7	$158.72	11.169%	$176.4474	$176.45	$176.45	$176.40
7 purchase totals =	$1,128.56		$1,248.6931	$1,248.69	$1,248.75	$1,248.50