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	$243.28	9.306%	$265.9196	$265.92	$265.90	$265.90
Purchase #2	$227.59	11.853%	$254.5662	$254.57	$254.55	$254.60
Purchase #3	$87.73	8.855%	$95.4985	$95.50	$95.50	$95.50
Purchase #4	$182.94	7.294%	$196.2836	$196.28	$196.30	$196.30
Purchase #5	$38.49	13.193%	$43.568	$43.57	$43.55	$43.60
Purchase #6	$28.79	4.349%	$30.0421	$30.04	$30.05	$30.00
Purchase #7	$100.44	13.630%	$114.13	$114.13	$114.15	$114.10
7 purchase totals =	$909.26		$1,000.0080	$1,000.01	$1,000.00	$1,000.00