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	$104.84	4.256%	$109.302	$109.30	$109.30	$109.30
Purchase #2	$51.93	11.601%	$57.9544	$57.95	$57.95	$58.00
Purchase #3	$240.40	6.492%	$256.0068	$256.01	$256.00	$256.00
Purchase #4	$104.49	12.331%	$117.3747	$117.37	$117.35	$117.40
Purchase #5	$15.78	13.320%	$17.8819	$17.88	$17.90	$17.90
Purchase #6	$214.40	6.260%	$227.8214	$227.82	$227.80	$227.80
Purchase #7	$244.57	12.602%	$275.3907	$275.39	$275.40	$275.40
7 purchase totals =	$976.41		$1,061.7319	$1,061.72	$1,061.70	$1,061.80