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	$199.30	10.593%	$220.4118	$220.41	$220.40	$220.40
Purchase #2	$172.40	7.237%	$184.8766	$184.88	$184.90	$184.90
Purchase #3	$97.45	12.330%	$109.4656	$109.47	$109.45	$109.50
Purchase #4	$177.84	12.300%	$199.7143	$199.71	$199.70	$199.70
Purchase #5	$95.59	10.712%	$105.8296	$105.83	$105.85	$105.80
Purchase #6	$61.85	13.387%	$70.1299	$70.13	$70.15	$70.10
Purchase #7	$62.81	12.436%	$70.6211	$70.62	$70.60	$70.60
7 purchase totals =	$867.24		$961.0489	$961.05	$961.05	$961.00