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	$32.61	5.639%	$34.4489	$34.45	$34.45	$34.40
Purchase #2	$225.56	3.690%	$233.8832	$233.88	$233.90	$233.90
Purchase #3	$44.90	3.276%	$46.3709	$46.37	$46.35	$46.40
Purchase #4	$218.89	11.859%	$244.8482	$244.85	$244.85	$244.80
Purchase #5	$161.36	4.329%	$168.3453	$168.35	$168.35	$168.30
Purchase #6	$250.33	9.697%	$274.6045	$274.60	$274.60	$274.60
Purchase #7	$136.75	10.725%	$151.4164	$151.42	$151.40	$151.40
7 purchase totals =	$1,070.40		$1,153.9174	$1,153.92	$1,153.90	$1,153.80