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	$96.80	7.591%	$104.1481	$104.15	$104.15	$104.10
Purchase #2	$27.73	10.659%	$30.6857	$30.69	$30.70	$30.70
Purchase #3	$38.65	7.304%	$41.473	$41.47	$41.45	$41.50
Purchase #4	$63.92	4.674%	$66.9076	$66.91	$66.90	$66.90
Purchase #5	$190.95	13.259%	$216.2681	$216.27	$216.25	$216.30
Purchase #6	$50.73	5.675%	$53.6089	$53.61	$53.60	$53.60
Purchase #7	$51.61	9.250%	$56.3839	$56.38	$56.40	$56.40
7 purchase totals =	$520.39		$569.4753	$569.48	$569.45	$569.50