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	$47.75	10.401%	$52.7165	$52.72	$52.70	$52.70
Purchase #2	$169.29	7.872%	$182.6165	$182.62	$182.60	$182.60
Purchase #3	$146.48	13.680%	$166.5185	$166.52	$166.50	$166.50
Purchase #4	$139.65	12.621%	$157.2752	$157.28	$157.30	$157.30
Purchase #5	$205.72	4.327%	$214.6215	$214.62	$214.60	$214.60
Purchase #6	$177.57	5.823%	$187.9099	$187.91	$187.90	$187.90
Purchase #7	$55.28	7.419%	$59.3812	$59.38	$59.40	$59.40
7 purchase totals =	$941.74		$1,021.0393	$1,021.05	$1,021.00	$1,021.00