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	$70.53	3.737%	$73.1657	$73.17	$73.15	$73.20
Purchase #2	$209.47	13.624%	$238.0082	$238.01	$238.00	$238.00
Purchase #3	$47.88	12.772%	$53.9952	$54.00	$54.00	$54.00
Purchase #4	$38.76	4.313%	$40.4317	$40.43	$40.45	$40.40
Purchase #5	$232.69	7.456%	$250.0394	$250.04	$250.05	$250.00
Purchase #6	$43.32	12.537%	$48.751	$48.75	$48.75	$48.80
Purchase #7	$20.89	4.431%	$21.8156	$21.82	$21.80	$21.80
7 purchase totals =	$663.54		$726.2068	$726.22	$726.20	$726.20