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	$58.93	6.468%	$62.7416	$62.74	$62.75	$62.70
Purchase #2	$48.76	6.432%	$51.8962	$51.90	$51.90	$51.90
Purchase #3	$51.87	7.701%	$55.8645	$55.86	$55.85	$55.90
Purchase #4	$190.52	13.559%	$216.3526	$216.35	$216.35	$216.40
Purchase #5	$11.92	11.586%	$13.3011	$13.30	$13.30	$13.30
Purchase #6	$7.39	5.509%	$7.7971	$7.80	$7.80	$7.80
Purchase #7	$141.38	8.384%	$153.2333	$153.23	$153.25	$153.20
7 purchase totals =	$510.77		$561.1864	$561.18	$561.20	$561.20