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	$60.85	10.554%	$67.2721	$67.27	$67.25	$67.30
Purchase #2	$94.99	8.820%	$103.3681	$103.37	$103.35	$103.40
Purchase #3	$189.51	10.325%	$209.0769	$209.08	$209.10	$209.10
Purchase #4	$64.99	13.669%	$73.8735	$73.87	$73.85	$73.90
Purchase #5	$94.51	11.835%	$105.6953	$105.70	$105.70	$105.70
Purchase #6	$187.46	4.735%	$196.3362	$196.34	$196.35	$196.30
Purchase #7	$67.98	11.373%	$75.7114	$75.71	$75.70	$75.70
7 purchase totals =	$760.29		$831.3335	$831.34	$831.30	$831.40