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	$234.27	8.731%	$254.7241	$254.72	$254.70	$254.70
Purchase #2	$9.59	10.412%	$10.5885	$10.59	$10.60	$10.60
Purchase #3	$224.43	12.855%	$253.2805	$253.28	$253.30	$253.30
Purchase #4	$247.84	7.534%	$266.5123	$266.51	$266.50	$266.50
Purchase #5	$119.53	9.789%	$131.2308	$131.23	$131.25	$131.20
Purchase #6	$213.47	4.213%	$222.4635	$222.46	$222.45	$222.50
Purchase #7	$217.33	10.849%	$240.9081	$240.91	$240.90	$240.90
7 purchase totals =	$1,266.46		$1,379.7078	$1,379.70	$1,379.70	$1,379.70