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	$5.59	6.204%	$5.9368	$5.94	$5.95	$5.90
Purchase #2	$52.30	12.451%	$58.8119	$58.81	$58.80	$58.80
Purchase #3	$37.55	13.499%	$42.6189	$42.62	$42.60	$42.60
Purchase #4	$78.89	11.475%	$87.9426	$87.94	$87.95	$87.90
Purchase #5	$91.36	10.130%	$100.6148	$100.61	$100.60	$100.60
Purchase #6	$216.85	3.695%	$224.8626	$224.86	$224.85	$224.90
Purchase #7	$5.29	6.500%	$5.6339	$5.63	$5.65	$5.60
7 purchase totals =	$487.83		$526.4215	$526.41	$526.40	$526.30