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	$213.51	4.706%	$223.5578	$223.56	$223.55	$223.60
Purchase #2	$48.33	9.555%	$52.9479	$52.95	$52.95	$52.90
Purchase #3	$126.78	7.605%	$136.4216	$136.42	$136.40	$136.40
Purchase #4	$230.77	10.507%	$255.017	$255.02	$255.00	$255.00
Purchase #5	$193.55	3.544%	$200.4094	$200.41	$200.40	$200.40
Purchase #6	$209.73	13.724%	$238.5133	$238.51	$238.50	$238.50
Purchase #7	$70.78	8.863%	$77.0532	$77.05	$77.05	$77.10
7 purchase totals =	$1,093.45		$1,183.9202	$1,183.92	$1,183.85	$1,183.90