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	$35.64	4.621%	$37.2869	$37.29	$37.30	$37.30
Purchase #2	$161.83	11.134%	$179.8482	$179.85	$179.85	$179.80
Purchase #3	$242.34	8.155%	$262.1028	$262.10	$262.10	$262.10
Purchase #4	$189.64	9.127%	$206.9484	$206.95	$206.95	$206.90
Purchase #5	$66.62	9.186%	$72.7397	$72.74	$72.75	$72.70
Purchase #6	$53.71	6.412%	$57.1539	$57.15	$57.15	$57.20
Purchase #7	$10.37	10.805%	$11.4905	$11.49	$11.50	$11.50
7 purchase totals =	$760.15		$827.5704	$827.57	$827.60	$827.50