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	$143.35	5.692%	$151.5095	$151.51	$151.50	$151.50
Purchase #2	$129.41	7.525%	$139.1481	$139.15	$139.15	$139.10
Purchase #3	$70.48	11.364%	$78.4893	$78.49	$78.50	$78.50
Purchase #4	$83.51	4.456%	$87.2312	$87.23	$87.25	$87.20
Purchase #5	$199.69	3.167%	$206.0142	$206.01	$206.00	$206.00
Purchase #6	$133.31	7.210%	$142.9217	$142.92	$142.90	$142.90
Purchase #7	$220.62	4.750%	$231.0995	$231.10	$231.10	$231.10
7 purchase totals =	$980.37		$1,036.4135	$1,036.41	$1,036.40	$1,036.30