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	$54.89	7.802%	$59.1725	$59.17	$59.15	$59.20
Purchase #2	$118.66	3.140%	$122.3859	$122.39	$122.40	$122.40
Purchase #3	$221.58	12.441%	$249.1468	$249.15	$249.15	$249.10
Purchase #4	$28.51	3.283%	$29.446	$29.45	$29.45	$29.40
Purchase #5	$33.84	10.291%	$37.3225	$37.32	$37.30	$37.30
Purchase #6	$41.65	10.770%	$46.1357	$46.14	$46.15	$46.10
Purchase #7	$201.87	7.436%	$216.8811	$216.88	$216.90	$216.90
7 purchase totals =	$701.00		$760.4905	$760.50	$760.50	$760.40