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	$197.66	7.541%	$212.5655	$212.57	$212.55	$212.60
Purchase #2	$191.83	11.858%	$214.5772	$214.58	$214.60	$214.60
Purchase #3	$20.50	7.803%	$22.0996	$22.10	$22.10	$22.10
Purchase #4	$160.43	7.660%	$172.7189	$172.72	$172.70	$172.70
Purchase #5	$140.56	11.587%	$156.8467	$156.85	$156.85	$156.80
Purchase #6	$219.28	3.763%	$227.5315	$227.53	$227.55	$227.50
Purchase #7	$117.58	5.374%	$123.8987	$123.90	$123.90	$123.90
7 purchase totals =	$1,047.84		$1,130.2381	$1,130.25	$1,130.25	$1,130.20