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	$231.38	6.864%	$247.2619	$247.26	$247.25	$247.30
Purchase #2	$57.97	6.729%	$61.8708	$61.87	$61.85	$61.90
Purchase #3	$130.48	3.214%	$134.6736	$134.67	$134.65	$134.70
Purchase #4	$153.35	8.327%	$166.1195	$166.12	$166.10	$166.10
Purchase #5	$157.42	9.822%	$172.8818	$172.88	$172.90	$172.90
Purchase #6	$171.83	5.609%	$181.4679	$181.47	$181.45	$181.50
Purchase #7	$35.46	8.873%	$38.6064	$38.61	$38.60	$38.60
7 purchase totals =	$937.89		$1,002.8819	$1,002.88	$1,002.80	$1,003.00