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	$116.82	6.549%	$124.4705	$124.47	$124.45	$124.50
Purchase #2	$16.85	6.389%	$17.9265	$17.93	$17.95	$17.90
Purchase #3	$104.50	10.212%	$115.1715	$115.17	$115.15	$115.20
Purchase #4	$81.53	5.308%	$85.8576	$85.86	$85.85	$85.90
Purchase #5	$16.88	9.176%	$18.4289	$18.43	$18.45	$18.40
Purchase #6	$106.38	3.354%	$109.948	$109.95	$109.95	$109.90
Purchase #7	$36.65	6.749%	$39.1235	$39.12	$39.10	$39.10
7 purchase totals =	$479.61		$510.9265	$510.93	$510.90	$510.90