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	$63.66	6.620%	$67.8743	$67.87	$67.85	$67.90
Purchase #2	$132.88	10.243%	$146.4909	$146.49	$146.50	$146.50
Purchase #3	$119.59	9.615%	$131.0886	$131.09	$131.10	$131.10
Purchase #4	$226.95	7.365%	$243.6649	$243.66	$243.65	$243.70
Purchase #5	$78.42	10.302%	$86.4988	$86.50	$86.50	$86.50
Purchase #6	$128.55	12.410%	$144.5031	$144.50	$144.50	$144.50
Purchase #7	$205.39	4.368%	$214.3614	$214.36	$214.35	$214.40
7 purchase totals =	$955.44		$1,034.4820	$1,034.47	$1,034.45	$1,034.60