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	$83.25	11.484%	$92.8104	$92.81	$92.80	$92.80
Purchase #2	$18.83	8.185%	$20.3712	$20.37	$20.35	$20.40
Purchase #3	$133.76	7.674%	$144.0247	$144.02	$144.00	$144.00
Purchase #4	$147.93	6.291%	$157.2363	$157.24	$157.25	$157.20
Purchase #5	$155.97	11.652%	$174.1436	$174.14	$174.15	$174.10
Purchase #6	$146.26	6.328%	$155.5153	$155.52	$155.50	$155.50
Purchase #7	$228.56	12.222%	$256.4946	$256.49	$256.50	$256.50
7 purchase totals =	$914.56		$1,000.5961	$1,000.59	$1,000.55	$1,000.50