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	$59.61	6.306%	$63.369	$63.37	$63.35	$63.40
Purchase #2	$84.29	4.751%	$88.2946	$88.29	$88.30	$88.30
Purchase #3	$34.86	10.266%	$38.4387	$38.44	$38.45	$38.40
Purchase #4	$127.55	12.765%	$143.8318	$143.83	$143.85	$143.80
Purchase #5	$52.53	3.719%	$54.4836	$54.48	$54.50	$54.50
Purchase #6	$75.31	6.579%	$80.2646	$80.26	$80.25	$80.30
Purchase #7	$97.69	4.318%	$101.9083	$101.91	$101.90	$101.90
7 purchase totals =	$531.84		$570.5906	$570.58	$570.60	$570.60