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	$194.32	13.106%	$219.7876	$219.79	$219.80	$219.80
Purchase #2	$81.27	11.306%	$90.4584	$90.46	$90.45	$90.50
Purchase #3	$50.32	12.718%	$56.7197	$56.72	$56.70	$56.70
Purchase #4	$25.80	6.662%	$27.5188	$27.52	$27.50	$27.50
Purchase #5	$54.41	7.181%	$58.3172	$58.32	$58.30	$58.30
Purchase #6	$155.74	10.657%	$172.3372	$172.34	$172.35	$172.30
Purchase #7	$165.47	7.244%	$177.4566	$177.46	$177.45	$177.50
7 purchase totals =	$727.33		$802.5955	$802.61	$802.55	$802.60