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	$58.73	9.527%	$64.3252	$64.33	$64.35	$64.30
Purchase #2	$197.83	10.583%	$218.7663	$218.77	$218.75	$218.80
Purchase #3	$250.81	6.166%	$266.2749	$266.27	$266.25	$266.30
Purchase #4	$61.46	5.298%	$64.7162	$64.72	$64.70	$64.70
Purchase #5	$78.90	11.446%	$87.9309	$87.93	$87.95	$87.90
Purchase #6	$238.81	10.746%	$264.4725	$264.47	$264.45	$264.50
Purchase #7	$119.41	3.788%	$123.9333	$123.93	$123.95	$123.90
7 purchase totals =	$1,005.95		$1,090.4193	$1,090.42	$1,090.40	$1,090.40