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	$45.93	5.807%	$48.5972	$48.60	$48.60	$48.60
Purchase #2	$133.62	7.407%	$143.5172	$143.52	$143.50	$143.50
Purchase #3	$233.94	7.500%	$251.4855	$251.49	$251.50	$251.50
Purchase #4	$34.78	8.192%	$37.6292	$37.63	$37.65	$37.60
Purchase #5	$70.82	12.196%	$79.4572	$79.46	$79.45	$79.50
Purchase #6	$69.40	4.412%	$72.4619	$72.46	$72.45	$72.50
Purchase #7	$173.95	10.311%	$191.886	$191.89	$191.90	$191.90
7 purchase totals =	$762.44		$825.0342	$825.05	$825.05	$825.10