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	$101.71	6.611%	$108.434	$108.43	$108.45	$108.40
Purchase #2	$112.67	5.689%	$119.0798	$119.08	$119.10	$119.10
Purchase #3	$95.72	11.549%	$106.7747	$106.77	$106.75	$106.80
Purchase #4	$215.38	4.441%	$224.945	$224.95	$224.95	$224.90
Purchase #5	$82.61	7.553%	$88.8495	$88.85	$88.85	$88.80
Purchase #6	$74.49	12.667%	$83.9256	$83.93	$83.95	$83.90
Purchase #7	$52.86	11.821%	$59.1086	$59.11	$59.10	$59.10
7 purchase totals =	$735.44		$791.1172	$791.12	$791.15	$791.00