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	$217.90	8.854%	$237.1929	$237.19	$237.20	$237.20
Purchase #2	$100.38	12.215%	$112.6414	$112.64	$112.65	$112.60
Purchase #3	$152.42	12.274%	$171.128	$171.13	$171.15	$171.10
Purchase #4	$73.82	12.345%	$82.9331	$82.93	$82.95	$82.90
Purchase #5	$69.43	7.182%	$74.4165	$74.42	$74.40	$74.40
Purchase #6	$151.96	3.833%	$157.7846	$157.78	$157.80	$157.80
Purchase #7	$19.38	4.410%	$20.2347	$20.23	$20.25	$20.20
7 purchase totals =	$785.29		$856.3312	$856.32	$856.40	$856.20