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	$127.37	12.486%	$143.2734	$143.27	$143.25	$143.30
Purchase #2	$148.62	13.342%	$168.4489	$168.45	$168.45	$168.40
Purchase #3	$215.89	12.527%	$242.9345	$242.93	$242.95	$242.90
Purchase #4	$204.44	12.273%	$229.5309	$229.53	$229.55	$229.50
Purchase #5	$246.38	11.795%	$275.4405	$275.44	$275.45	$275.40
Purchase #6	$248.51	8.692%	$270.1105	$270.11	$270.10	$270.10
Purchase #7	$152.83	8.474%	$165.7808	$165.78	$165.80	$165.80
7 purchase totals =	$1,344.04		$1,495.5195	$1,495.51	$1,495.55	$1,495.40