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	$234.49	10.752%	$259.7024	$259.70	$259.70	$259.70
Purchase #2	$178.76	9.862%	$196.3893	$196.39	$196.40	$196.40
Purchase #3	$87.63	13.757%	$99.6853	$99.69	$99.70	$99.70
Purchase #4	$104.88	11.780%	$117.2349	$117.23	$117.25	$117.20
Purchase #5	$164.78	12.196%	$184.8766	$184.88	$184.90	$184.90
Purchase #6	$36.61	11.321%	$40.7546	$40.75	$40.75	$40.80
Purchase #7	$152.54	8.511%	$165.5227	$165.52	$165.50	$165.50
7 purchase totals =	$959.69		$1,064.1658	$1,064.16	$1,064.20	$1,064.20