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	$136.34	12.139%	$152.8903	$152.89	$152.90	$152.90
Purchase #2	$22.91	8.723%	$24.9084	$24.91	$24.90	$24.90
Purchase #3	$19.68	5.714%	$20.8045	$20.80	$20.80	$20.80
Purchase #4	$187.93	4.290%	$195.9922	$195.99	$196.00	$196.00
Purchase #5	$70.72	7.656%	$76.1343	$76.13	$76.15	$76.10
Purchase #6	$73.40	13.348%	$83.1974	$83.20	$83.20	$83.20
Purchase #7	$161.94	6.782%	$172.9228	$172.92	$172.90	$172.90
7 purchase totals =	$672.92		$726.8499	$726.84	$726.85	$726.80