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	$91.29	12.771%	$102.9486	$102.95	$102.95	$102.90
Purchase #2	$211.29	5.339%	$222.5708	$222.57	$222.55	$222.60
Purchase #3	$146.97	10.410%	$162.2696	$162.27	$162.25	$162.30
Purchase #4	$58.68	13.124%	$66.3812	$66.38	$66.40	$66.40
Purchase #5	$149.76	12.801%	$168.9308	$168.93	$168.95	$168.90
Purchase #6	$76.76	6.371%	$81.6504	$81.65	$81.65	$81.70
Purchase #7	$38.50	11.282%	$42.8436	$42.84	$42.85	$42.80
7 purchase totals =	$773.25		$847.5950	$847.59	$847.60	$847.60