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	$207.66	7.266%	$222.7486	$222.75	$222.75	$222.70
Purchase #2	$190.69	13.855%	$217.1101	$217.11	$217.10	$217.10
Purchase #3	$89.96	11.192%	$100.0283	$100.03	$100.05	$100.00
Purchase #4	$79.37	5.504%	$83.7385	$83.74	$83.75	$83.70
Purchase #5	$65.48	7.333%	$70.2816	$70.28	$70.30	$70.30
Purchase #6	$65.61	7.106%	$70.2722	$70.27	$70.25	$70.30
Purchase #7	$121.86	12.808%	$137.4678	$137.47	$137.45	$137.50
7 purchase totals =	$820.63		$901.6471	$901.65	$901.65	$901.60