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	$126.98	11.679%	$141.81	$141.81	$141.80	$141.80
Purchase #2	$95.73	3.503%	$99.0834	$99.08	$99.10	$99.10
Purchase #3	$202.26	8.664%	$219.7838	$219.78	$219.80	$219.80
Purchase #4	$53.28	10.800%	$59.0342	$59.03	$59.05	$59.00
Purchase #5	$142.64	9.766%	$156.5702	$156.57	$156.55	$156.60
Purchase #6	$56.73	3.650%	$58.8006	$58.80	$58.80	$58.80
Purchase #7	$163.45	9.562%	$179.0791	$179.08	$179.10	$179.10
7 purchase totals =	$841.07		$914.1613	$914.15	$914.20	$914.20