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	$75.62	10.773%	$83.7665	$83.77	$83.75	$83.80
Purchase #2	$38.46	6.567%	$40.9857	$40.99	$41.00	$41.00
Purchase #3	$205.76	4.422%	$214.8587	$214.86	$214.85	$214.90
Purchase #4	$68.70	10.780%	$76.1059	$76.11	$76.10	$76.10
Purchase #5	$33.31	11.497%	$37.1397	$37.14	$37.15	$37.10
Purchase #6	$37.37	13.216%	$42.3088	$42.31	$42.30	$42.30
Purchase #7	$199.56	11.635%	$222.7788	$222.78	$222.80	$222.80
7 purchase totals =	$658.78		$717.9441	$717.96	$717.95	$718.00