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	$126.89	12.445%	$142.6815	$142.68	$142.70	$142.70
Purchase #2	$15.92	3.523%	$16.4809	$16.48	$16.50	$16.50
Purchase #3	$29.58	10.385%	$32.6519	$32.65	$32.65	$32.70
Purchase #4	$196.97	10.362%	$217.38	$217.38	$217.40	$217.40
Purchase #5	$170.45	10.470%	$188.2961	$188.30	$188.30	$188.30
Purchase #6	$104.85	11.160%	$116.5513	$116.55	$116.55	$116.60
Purchase #7	$189.86	5.534%	$200.3669	$200.37	$200.35	$200.40
7 purchase totals =	$834.52		$914.4086	$914.41	$914.45	$914.60