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	$132.74	9.602%	$145.4857	$145.49	$145.50	$145.50
Purchase #2	$217.67	5.155%	$228.8909	$228.89	$228.90	$228.90
Purchase #3	$168.81	12.285%	$189.5483	$189.55	$189.55	$189.50
Purchase #4	$209.57	13.836%	$238.5661	$238.57	$238.55	$238.60
Purchase #5	$118.41	7.530%	$127.3263	$127.33	$127.35	$127.30
Purchase #6	$9.89	6.849%	$10.5674	$10.57	$10.55	$10.60
Purchase #7	$87.91	7.368%	$94.3872	$94.39	$94.40	$94.40
7 purchase totals =	$945.00		$1,034.7719	$1,034.79	$1,034.80	$1,034.80