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	$180.57	10.532%	$199.5876	$199.59	$199.60	$199.60
Purchase #2	$102.59	6.277%	$109.0296	$109.03	$109.05	$109.00
Purchase #3	$43.81	9.821%	$48.1126	$48.11	$48.10	$48.10
Purchase #4	$177.89	12.334%	$199.831	$199.83	$199.85	$199.80
Purchase #5	$30.91	10.745%	$34.2313	$34.23	$34.25	$34.20
Purchase #6	$236.77	11.860%	$264.8509	$264.85	$264.85	$264.90
Purchase #7	$95.66	5.140%	$100.5769	$100.58	$100.60	$100.60
7 purchase totals =	$868.20		$956.2199	$956.22	$956.30	$956.20