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	$189.30	3.811%	$196.5142	$196.51	$196.50	$196.50
Purchase #2	$31.81	3.346%	$32.8744	$32.87	$32.85	$32.90
Purchase #3	$38.40	5.405%	$40.4755	$40.48	$40.50	$40.50
Purchase #4	$154.79	6.720%	$165.1919	$165.19	$165.20	$165.20
Purchase #5	$38.86	11.121%	$43.1816	$43.18	$43.20	$43.20
Purchase #6	$56.66	13.548%	$64.3363	$64.34	$64.35	$64.30
Purchase #7	$246.96	4.709%	$258.5893	$258.59	$258.60	$258.60
7 purchase totals =	$756.78		$801.1632	$801.16	$801.20	$801.20