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	$36.29	12.544%	$40.8422	$40.84	$40.85	$40.80
Purchase #2	$42.88	12.104%	$48.0702	$48.07	$48.05	$48.10
Purchase #3	$64.30	12.395%	$72.27	$72.27	$72.25	$72.30
Purchase #4	$143.98	9.399%	$157.5127	$157.51	$157.50	$157.50
Purchase #5	$57.65	6.141%	$61.1903	$61.19	$61.20	$61.20
Purchase #6	$72.68	5.147%	$76.4208	$76.42	$76.40	$76.40
Purchase #7	$211.46	12.622%	$238.1505	$238.15	$238.15	$238.20
7 purchase totals =	$629.24		$694.4567	$694.45	$694.40	$694.50