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	$33.33	3.419%	$34.4696	$34.47	$34.45	$34.50
Purchase #2	$190.89	12.459%	$214.673	$214.67	$214.65	$214.70
Purchase #3	$159.39	3.526%	$165.0101	$165.01	$165.00	$165.00
Purchase #4	$199.58	12.862%	$225.25	$225.25	$225.25	$225.30
Purchase #5	$122.80	6.711%	$131.0411	$131.04	$131.05	$131.00
Purchase #6	$112.85	9.368%	$123.4218	$123.42	$123.40	$123.40
Purchase #7	$169.26	10.186%	$186.5008	$186.50	$186.50	$186.50
7 purchase totals =	$988.10		$1,080.3664	$1,080.36	$1,080.30	$1,080.40