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	$30.88	5.661%	$32.6281	$32.63	$32.65	$32.60
Purchase #2	$155.84	8.817%	$169.5804	$169.58	$169.60	$169.60
Purchase #3	$165.94	3.499%	$171.7462	$171.75	$171.75	$171.70
Purchase #4	$108.55	10.226%	$119.6503	$119.65	$119.65	$119.70
Purchase #5	$133.78	5.796%	$141.5339	$141.53	$141.55	$141.50
Purchase #6	$13.35	11.530%	$14.8893	$14.89	$14.90	$14.90
Purchase #7	$122.96	13.365%	$139.3936	$139.39	$139.40	$139.40
7 purchase totals =	$731.30		$789.4218	$789.42	$789.50	$789.40