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	$141.43	5.530%	$149.2511	$149.25	$149.25	$149.30
Purchase #2	$113.96	8.359%	$123.4859	$123.49	$123.50	$123.50
Purchase #3	$32.49	11.650%	$36.2751	$36.28	$36.30	$36.30
Purchase #4	$13.66	10.735%	$15.1264	$15.13	$15.15	$15.10
Purchase #5	$87.49	3.438%	$90.4979	$90.50	$90.50	$90.50
Purchase #6	$105.54	12.428%	$118.6565	$118.66	$118.65	$118.70
Purchase #7	$91.45	3.723%	$94.8547	$94.85	$94.85	$94.90
7 purchase totals =	$586.02		$628.1476	$628.16	$628.20	$628.30