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	$172.39	7.580%	$185.4572	$185.46	$185.45	$185.50
Purchase #2	$206.84	13.582%	$234.933	$234.93	$234.95	$234.90
Purchase #3	$237.96	4.212%	$247.9829	$247.98	$248.00	$248.00
Purchase #4	$145.77	10.560%	$161.1633	$161.16	$161.15	$161.20
Purchase #5	$71.73	9.401%	$78.4733	$78.47	$78.45	$78.50
Purchase #6	$10.85	11.430%	$12.0902	$12.09	$12.10	$12.10
Purchase #7	$196.49	10.314%	$216.756	$216.76	$216.75	$216.80
7 purchase totals =	$1,042.03		$1,136.8559	$1,136.85	$1,136.85	$1,137.00