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	$201.96	3.814%	$209.6628	$209.66	$209.65	$209.70
Purchase #2	$80.83	6.169%	$85.8164	$85.82	$85.80	$85.80
Purchase #3	$65.51	9.674%	$71.8474	$71.85	$71.85	$71.80
Purchase #4	$150.40	9.387%	$164.518	$164.52	$164.50	$164.50
Purchase #5	$153.39	9.775%	$168.3839	$168.38	$168.40	$168.40
Purchase #6	$111.80	4.449%	$116.774	$116.77	$116.75	$116.80
Purchase #7	$35.97	10.683%	$39.8127	$39.81	$39.80	$39.80
7 purchase totals =	$799.86		$856.8152	$856.81	$856.75	$856.80