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	$145.53	10.512%	$160.8281	$160.83	$160.85	$160.80
Purchase #2	$53.52	13.667%	$60.8346	$60.83	$60.85	$60.80
Purchase #3	$242.79	4.488%	$253.6864	$253.69	$253.70	$253.70
Purchase #4	$118.51	12.306%	$133.0938	$133.09	$133.10	$133.10
Purchase #5	$156.58	11.761%	$174.9954	$175.00	$175.00	$175.00
Purchase #6	$50.96	3.743%	$52.8674	$52.87	$52.85	$52.90
Purchase #7	$237.67	7.506%	$255.5095	$255.51	$255.50	$255.50
7 purchase totals =	$1,005.56		$1,091.8152	$1,091.82	$1,091.85	$1,091.80