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	$65.67	6.243%	$69.7698	$69.77	$69.75	$69.80
Purchase #2	$221.35	7.851%	$238.7282	$238.73	$238.75	$238.70
Purchase #3	$72.57	6.422%	$77.2304	$77.23	$77.25	$77.20
Purchase #4	$42.30	7.513%	$45.478	$45.48	$45.50	$45.50
Purchase #5	$137.96	5.700%	$145.8237	$145.82	$145.80	$145.80
Purchase #6	$43.65	10.440%	$48.2071	$48.21	$48.20	$48.20
Purchase #7	$162.59	3.802%	$168.7717	$168.77	$168.75	$168.80
7 purchase totals =	$746.09		$794.0089	$794.01	$794.00	$794.00