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	$141.76	13.401%	$160.7573	$160.76	$160.75	$160.80
Purchase #2	$118.62	8.289%	$128.4524	$128.45	$128.45	$128.50
Purchase #3	$173.25	13.403%	$196.4707	$196.47	$196.45	$196.50
Purchase #4	$36.81	5.232%	$38.7359	$38.74	$38.75	$38.70
Purchase #5	$112.73	4.551%	$117.8603	$117.86	$117.85	$117.90
Purchase #6	$45.84	12.262%	$51.4609	$51.46	$51.45	$51.50
Purchase #7	$227.37	8.319%	$246.2849	$246.28	$246.30	$246.30
7 purchase totals =	$856.38		$940.0224	$940.02	$940.00	$940.20