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	$165.93	4.341%	$173.133	$173.13	$173.15	$173.10
Purchase #2	$178.46	8.713%	$194.0092	$194.01	$194.00	$194.00
Purchase #3	$141.41	7.486%	$151.996	$152.00	$152.00	$152.00
Purchase #4	$59.88	7.684%	$64.4812	$64.48	$64.50	$64.50
Purchase #5	$200.26	13.545%	$227.3852	$227.39	$227.40	$227.40
Purchase #6	$95.25	8.682%	$103.5196	$103.52	$103.50	$103.50
Purchase #7	$242.82	9.500%	$265.8879	$265.89	$265.90	$265.90
7 purchase totals =	$1,084.01		$1,180.4121	$1,180.42	$1,180.45	$1,180.40