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	$47.66	10.866%	$52.8387	$52.84	$52.85	$52.80
Purchase #2	$193.95	9.219%	$211.8303	$211.83	$211.85	$211.80
Purchase #3	$234.56	5.261%	$246.9002	$246.90	$246.90	$246.90
Purchase #4	$181.32	8.401%	$196.5527	$196.55	$196.55	$196.60
Purchase #5	$172.30	11.163%	$191.5338	$191.53	$191.55	$191.50
Purchase #6	$127.97	4.637%	$133.904	$133.90	$133.90	$133.90
Purchase #7	$34.33	10.178%	$37.8241	$37.82	$37.80	$37.80
7 purchase totals =	$992.09		$1,071.3838	$1,071.37	$1,071.40	$1,071.30