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	$191.29	5.719%	$202.2299	$202.23	$202.25	$202.20
Purchase #2	$31.33	6.681%	$33.4232	$33.42	$33.40	$33.40
Purchase #3	$99.62	5.286%	$104.8859	$104.89	$104.90	$104.90
Purchase #4	$116.48	13.659%	$132.39	$132.39	$132.40	$132.40
Purchase #5	$39.91	7.167%	$42.7703	$42.77	$42.75	$42.80
Purchase #6	$149.48	9.741%	$164.0408	$164.04	$164.05	$164.00
Purchase #7	$37.72	11.421%	$42.028	$42.03	$42.05	$42.00
7 purchase totals =	$665.83		$721.7681	$721.77	$721.80	$721.70