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	$181.25	4.436%	$189.2903	$189.29	$189.30	$189.30
Purchase #2	$125.42	4.460%	$131.0137	$131.01	$131.00	$131.00
Purchase #3	$146.28	4.360%	$152.6578	$152.66	$152.65	$152.70
Purchase #4	$84.66	3.817%	$87.8915	$87.89	$87.90	$87.90
Purchase #5	$121.71	11.856%	$136.1399	$136.14	$136.15	$136.10
Purchase #6	$34.47	7.787%	$37.1542	$37.15	$37.15	$37.20
Purchase #7	$70.79	10.710%	$78.3716	$78.37	$78.35	$78.40
7 purchase totals =	$764.58		$812.5190	$812.51	$812.50	$812.60