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	$110.35	7.408%	$118.5247	$118.52	$118.50	$118.50
Purchase #2	$27.44	13.289%	$31.0865	$31.09	$31.10	$31.10
Purchase #3	$174.88	3.264%	$180.5881	$180.59	$180.60	$180.60
Purchase #4	$139.34	12.264%	$156.4287	$156.43	$156.45	$156.40
Purchase #5	$206.87	11.130%	$229.8946	$229.89	$229.90	$229.90
Purchase #6	$163.27	3.193%	$168.4832	$168.48	$168.50	$168.50
Purchase #7	$177.46	5.621%	$187.435	$187.44	$187.45	$187.40
7 purchase totals =	$999.61		$1,072.4408	$1,072.44	$1,072.50	$1,072.40