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	$71.96	3.471%	$74.4577	$74.46	$74.45	$74.50
Purchase #2	$105.57	4.732%	$110.5656	$110.57	$110.55	$110.60
Purchase #3	$196.34	12.413%	$220.7117	$220.71	$220.70	$220.70
Purchase #4	$173.45	10.262%	$191.2494	$191.25	$191.25	$191.20
Purchase #5	$118.70	12.561%	$133.6099	$133.61	$133.60	$133.60
Purchase #6	$100.87	8.566%	$109.5105	$109.51	$109.50	$109.50
Purchase #7	$11.89	8.113%	$12.8546	$12.85	$12.85	$12.90
7 purchase totals =	$778.78		$852.9594	$852.96	$852.90	$853.00