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	$239.89	8.704%	$260.77	$260.77	$260.75	$260.80
Purchase #2	$76.49	12.285%	$85.8868	$85.89	$85.90	$85.90
Purchase #3	$102.82	11.143%	$114.2772	$114.28	$114.30	$114.30
Purchase #4	$109.94	12.654%	$123.8518	$123.85	$123.85	$123.90
Purchase #5	$241.44	3.692%	$250.354	$250.35	$250.35	$250.40
Purchase #6	$68.29	11.139%	$75.8968	$75.90	$75.90	$75.90
Purchase #7	$245.49	10.104%	$270.2943	$270.29	$270.30	$270.30
7 purchase totals =	$1,084.36		$1,181.3309	$1,181.33	$1,181.35	$1,181.50