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	$236.97	8.285%	$256.603	$256.60	$256.60	$256.60
Purchase #2	$225.77	12.203%	$253.3207	$253.32	$253.30	$253.30
Purchase #3	$233.89	13.770%	$266.0967	$266.10	$266.10	$266.10
Purchase #4	$188.94	11.417%	$210.5113	$210.51	$210.50	$210.50
Purchase #5	$96.97	13.315%	$109.8816	$109.88	$109.90	$109.90
Purchase #6	$96.47	11.417%	$107.484	$107.48	$107.50	$107.50
Purchase #7	$52.33	11.393%	$58.292	$58.29	$58.30	$58.30
7 purchase totals =	$1,131.34		$1,262.1893	$1,262.18	$1,262.20	$1,262.20