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	$194.60	10.800%	$215.6168	$215.62	$215.60	$215.60
Purchase #2	$80.96	10.517%	$89.4746	$89.47	$89.45	$89.50
Purchase #3	$75.46	12.203%	$84.6684	$84.67	$84.65	$84.70
Purchase #4	$82.25	13.392%	$93.2649	$93.26	$93.25	$93.30
Purchase #5	$153.97	9.645%	$168.8204	$168.82	$168.80	$168.80
Purchase #6	$48.84	5.287%	$51.4222	$51.42	$51.40	$51.40
Purchase #7	$6.75	10.574%	$7.4637	$7.46	$7.45	$7.50
7 purchase totals =	$642.83		$710.7310	$710.72	$710.60	$710.80