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	$169.39	12.233%	$190.1115	$190.11	$190.10	$190.10
Purchase #2	$82.83	4.327%	$86.4141	$86.41	$86.40	$86.40
Purchase #3	$60.86	3.623%	$63.065	$63.07	$63.05	$63.10
Purchase #4	$148.93	13.211%	$168.6051	$168.61	$168.60	$168.60
Purchase #5	$96.37	5.666%	$101.8303	$101.83	$101.85	$101.80
Purchase #6	$9.70	12.170%	$10.8805	$10.88	$10.90	$10.90
Purchase #7	$36.99	12.135%	$41.4787	$41.48	$41.50	$41.50
7 purchase totals =	$605.07		$662.3852	$662.39	$662.40	$662.40