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	$116.62	12.388%	$131.0669	$131.07	$131.05	$131.10
Purchase #2	$114.81	12.686%	$129.3748	$129.37	$129.35	$129.40
Purchase #3	$52.85	12.721%	$59.573	$59.57	$59.55	$59.60
Purchase #4	$224.61	5.487%	$236.9344	$236.93	$236.95	$236.90
Purchase #5	$171.32	6.755%	$182.8927	$182.89	$182.90	$182.90
Purchase #6	$246.67	6.464%	$262.6147	$262.61	$262.60	$262.60
Purchase #7	$153.56	7.440%	$164.9849	$164.98	$165.00	$165.00
7 purchase totals =	$1,080.44		$1,167.4414	$1,167.42	$1,167.40	$1,167.50