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	$136.33	5.869%	$144.3312	$144.33	$144.35	$144.30
Purchase #2	$160.72	4.833%	$168.4876	$168.49	$168.50	$168.50
Purchase #3	$81.60	5.811%	$86.3418	$86.34	$86.35	$86.30
Purchase #4	$32.87	4.352%	$34.3005	$34.30	$34.30	$34.30
Purchase #5	$176.89	11.189%	$196.6822	$196.68	$196.70	$196.70
Purchase #6	$22.26	12.724%	$25.0924	$25.09	$25.10	$25.10
Purchase #7	$135.53	9.414%	$148.2888	$148.29	$148.30	$148.30
7 purchase totals =	$746.20		$803.5245	$803.52	$803.60	$803.50