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	$193.70	11.246%	$215.4835	$215.48	$215.50	$215.50
Purchase #2	$243.47	5.400%	$256.6174	$256.62	$256.60	$256.60
Purchase #3	$129.39	6.168%	$137.3708	$137.37	$137.35	$137.40
Purchase #4	$9.44	9.336%	$10.3213	$10.32	$10.30	$10.30
Purchase #5	$202.57	7.352%	$217.4629	$217.46	$217.45	$217.50
Purchase #6	$93.25	3.514%	$96.5268	$96.53	$96.55	$96.50
Purchase #7	$81.30	11.653%	$90.7739	$90.77	$90.75	$90.80
7 purchase totals =	$953.12		$1,024.5566	$1,024.55	$1,024.50	$1,024.60