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	$130.72	12.803%	$147.4561	$147.46	$147.45	$147.50
Purchase #2	$38.64	11.409%	$43.0484	$43.05	$43.05	$43.00
Purchase #3	$12.65	7.806%	$13.6375	$13.64	$13.65	$13.60
Purchase #4	$75.94	8.603%	$82.4731	$82.47	$82.45	$82.50
Purchase #5	$185.43	13.857%	$211.125	$211.13	$211.15	$211.10
Purchase #6	$128.66	10.775%	$142.5231	$142.52	$142.50	$142.50
Purchase #7	$245.68	6.441%	$261.5042	$261.50	$261.50	$261.50
7 purchase totals =	$817.72		$901.7674	$901.77	$901.75	$901.70