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	$88.46	3.190%	$91.2819	$91.28	$91.30	$91.30
Purchase #2	$76.27	13.220%	$86.3529	$86.35	$86.35	$86.40
Purchase #3	$111.67	12.394%	$125.5104	$125.51	$125.50	$125.50
Purchase #4	$34.37	8.404%	$37.2585	$37.26	$37.25	$37.30
Purchase #5	$35.47	5.312%	$37.3542	$37.35	$37.35	$37.40
Purchase #6	$11.95	13.725%	$13.5901	$13.59	$13.60	$13.60
Purchase #7	$76.56	3.843%	$79.5022	$79.50	$79.50	$79.50
7 purchase totals =	$434.75		$470.8502	$470.84	$470.85	$471.00