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	$60.94	9.673%	$66.8347	$66.83	$66.85	$66.80
Purchase #2	$55.77	6.676%	$59.4932	$59.49	$59.50	$59.50
Purchase #3	$247.70	3.113%	$255.4109	$255.41	$255.40	$255.40
Purchase #4	$152.59	8.599%	$165.7112	$165.71	$165.70	$165.70
Purchase #5	$139.90	12.464%	$157.3371	$157.34	$157.35	$157.30
Purchase #6	$165.31	10.561%	$182.7684	$182.77	$182.75	$182.80
Purchase #7	$139.26	10.811%	$154.3154	$154.32	$154.30	$154.30
7 purchase totals =	$961.47		$1,041.8709	$1,041.87	$1,041.85	$1,041.80