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	$64.33	9.784%	$70.624	$70.62	$70.60	$70.60
Purchase #2	$247.79	13.226%	$280.5627	$280.56	$280.55	$280.60
Purchase #3	$66.93	5.186%	$70.401	$70.40	$70.40	$70.40
Purchase #4	$40.93	11.296%	$45.5535	$45.55	$45.55	$45.60
Purchase #5	$175.63	13.130%	$198.6902	$198.69	$198.70	$198.70
Purchase #6	$11.64	4.504%	$12.1643	$12.16	$12.15	$12.20
Purchase #7	$237.54	12.175%	$266.4605	$266.46	$266.45	$266.50
7 purchase totals =	$844.79		$944.4562	$944.44	$944.40	$944.60