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	$181.32	4.453%	$189.3942	$189.39	$189.40	$189.40
Purchase #2	$207.58	7.130%	$222.3805	$222.38	$222.40	$222.40
Purchase #3	$111.89	11.107%	$124.3176	$124.32	$124.30	$124.30
Purchase #4	$175.73	12.323%	$197.3852	$197.39	$197.40	$197.40
Purchase #5	$70.35	9.291%	$76.8862	$76.89	$76.90	$76.90
Purchase #6	$198.59	11.800%	$222.0236	$222.02	$222.00	$222.00
Purchase #7	$231.82	12.184%	$260.0649	$260.06	$260.05	$260.10
7 purchase totals =	$1,177.28		$1,292.4522	$1,292.45	$1,292.45	$1,292.50