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	$224.88	3.117%	$231.8895	$231.89	$231.90	$231.90
Purchase #2	$213.50	13.392%	$242.0919	$242.09	$242.10	$242.10
Purchase #3	$127.96	11.430%	$142.5858	$142.59	$142.60	$142.60
Purchase #4	$106.64	12.143%	$119.5893	$119.59	$119.60	$119.60
Purchase #5	$88.90	5.271%	$93.5859	$93.59	$93.60	$93.60
Purchase #6	$170.69	6.526%	$181.8292	$181.83	$181.85	$181.80
Purchase #7	$11.73	10.695%	$12.9845	$12.98	$13.00	$13.00
7 purchase totals =	$944.30		$1,024.5561	$1,024.56	$1,024.65	$1,024.60