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	$36.59	13.535%	$41.5425	$41.54	$41.55	$41.50
Purchase #2	$199.26	11.398%	$221.9717	$221.97	$221.95	$222.00
Purchase #3	$146.74	4.728%	$153.6779	$153.68	$153.70	$153.70
Purchase #4	$120.51	8.355%	$130.5786	$130.58	$130.60	$130.60
Purchase #5	$194.51	11.130%	$216.159	$216.16	$216.15	$216.20
Purchase #6	$116.72	12.662%	$131.4991	$131.50	$131.50	$131.50
Purchase #7	$157.89	5.311%	$166.2755	$166.28	$166.30	$166.30
7 purchase totals =	$972.22		$1,061.7043	$1,061.71	$1,061.75	$1,061.80