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	$126.66	11.606%	$141.3602	$141.36	$141.35	$141.40
Purchase #2	$33.72	6.364%	$35.8659	$35.87	$35.85	$35.90
Purchase #3	$151.72	9.365%	$165.9286	$165.93	$165.95	$165.90
Purchase #4	$246.89	10.509%	$272.8357	$272.84	$272.85	$272.80
Purchase #5	$73.44	6.316%	$78.0785	$78.08	$78.10	$78.10
Purchase #6	$238.69	9.842%	$262.1819	$262.18	$262.20	$262.20
Purchase #7	$70.63	8.854%	$76.8836	$76.88	$76.90	$76.90
7 purchase totals =	$941.75		$1,033.1344	$1,033.14	$1,033.20	$1,033.20