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	$169.51	7.659%	$182.4928	$182.49	$182.50	$182.50
Purchase #2	$108.53	3.863%	$112.7225	$112.72	$112.70	$112.70
Purchase #3	$190.40	12.544%	$214.2838	$214.28	$214.30	$214.30
Purchase #4	$247.89	11.308%	$275.9214	$275.92	$275.90	$275.90
Purchase #5	$159.61	7.697%	$171.8952	$171.90	$171.90	$171.90
Purchase #6	$193.76	12.390%	$217.7669	$217.77	$217.75	$217.80
Purchase #7	$143.89	12.838%	$162.3626	$162.36	$162.35	$162.40
7 purchase totals =	$1,213.59		$1,337.4452	$1,337.44	$1,337.40	$1,337.50