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	$180.29	10.735%	$199.6441	$199.64	$199.65	$199.60
Purchase #2	$132.37	12.763%	$149.2644	$149.26	$149.25	$149.30
Purchase #3	$192.41	10.447%	$212.5111	$212.51	$212.50	$212.50
Purchase #4	$95.79	4.216%	$99.8285	$99.83	$99.85	$99.80
Purchase #5	$192.75	11.340%	$214.6079	$214.61	$214.60	$214.60
Purchase #6	$16.97	9.358%	$18.5581	$18.56	$18.55	$18.60
Purchase #7	$161.80	5.766%	$171.1294	$171.13	$171.15	$171.10
7 purchase totals =	$972.38		$1,065.5435	$1,065.54	$1,065.55	$1,065.50