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	$111.36	7.365%	$119.5617	$119.56	$119.55	$119.60
Purchase #2	$54.83	8.287%	$59.3738	$59.37	$59.35	$59.40
Purchase #3	$160.66	11.843%	$179.687	$179.69	$179.70	$179.70
Purchase #4	$18.36	3.770%	$19.0522	$19.05	$19.05	$19.10
Purchase #5	$237.72	4.544%	$248.522	$248.52	$248.50	$248.50
Purchase #6	$165.25	6.426%	$175.869	$175.87	$175.85	$175.90
Purchase #7	$152.59	11.159%	$169.6175	$169.62	$169.60	$169.60
7 purchase totals =	$900.77		$971.6832	$971.68	$971.60	$971.80