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	$222.50	9.833%	$244.3784	$244.38	$244.40	$244.40
Purchase #2	$83.97	7.479%	$90.2501	$90.25	$90.25	$90.30
Purchase #3	$138.76	11.146%	$154.2262	$154.23	$154.25	$154.20
Purchase #4	$76.40	8.844%	$83.1568	$83.16	$83.15	$83.20
Purchase #5	$113.47	12.166%	$127.2748	$127.27	$127.25	$127.30
Purchase #6	$114.49	8.794%	$124.5583	$124.56	$124.55	$124.60
Purchase #7	$37.57	5.316%	$39.5672	$39.57	$39.55	$39.60
7 purchase totals =	$787.16		$863.4118	$863.42	$863.40	$863.60