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	$59.76	11.841%	$66.8362	$66.84	$66.85	$66.80
Purchase #2	$67.28	9.818%	$73.8856	$73.89	$73.90	$73.90
Purchase #3	$68.94	4.293%	$71.8996	$71.90	$71.90	$71.90
Purchase #4	$27.41	7.725%	$29.5274	$29.53	$29.55	$29.50
Purchase #5	$85.55	9.384%	$93.578	$93.58	$93.60	$93.60
Purchase #6	$239.36	4.184%	$249.3748	$249.37	$249.35	$249.40
Purchase #7	$30.73	10.293%	$33.893	$33.89	$33.90	$33.90
7 purchase totals =	$579.03		$618.9946	$619.00	$619.05	$619.00