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	$207.53	7.371%	$222.827	$222.83	$222.85	$222.80
Purchase #2	$198.80	12.209%	$223.0715	$223.07	$223.05	$223.10
Purchase #3	$61.68	6.135%	$65.4641	$65.46	$65.45	$65.50
Purchase #4	$240.35	13.474%	$272.7348	$272.73	$272.75	$272.70
Purchase #5	$75.78	10.167%	$83.4846	$83.48	$83.50	$83.50
Purchase #6	$236.78	10.179%	$260.8818	$260.88	$260.90	$260.90
Purchase #7	$50.61	7.590%	$54.4513	$54.45	$54.45	$54.50
7 purchase totals =	$1,071.53		$1,182.9151	$1,182.90	$1,182.95	$1,183.00