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	$137.68	6.472%	$146.5906	$146.59	$146.60	$146.60
Purchase #2	$98.32	10.189%	$108.3378	$108.34	$108.35	$108.30
Purchase #3	$85.54	12.823%	$96.5088	$96.51	$96.50	$96.50
Purchase #4	$100.80	8.381%	$109.248	$109.25	$109.25	$109.20
Purchase #5	$17.33	8.559%	$18.8133	$18.81	$18.80	$18.80
Purchase #6	$200.65	11.131%	$222.9844	$222.98	$223.00	$223.00
Purchase #7	$171.56	7.834%	$185	$185.00	$185.00	$185.00
7 purchase totals =	$811.88		$887.4829	$887.48	$887.50	$887.40