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	$86.37	13.659%	$98.1673	$98.17	$98.15	$98.20
Purchase #2	$57.82	9.653%	$63.4014	$63.40	$63.40	$63.40
Purchase #3	$85.49	3.595%	$88.5634	$88.56	$88.55	$88.60
Purchase #4	$140.61	13.575%	$159.6978	$159.70	$159.70	$159.70
Purchase #5	$50.89	11.356%	$56.6691	$56.67	$56.65	$56.70
Purchase #6	$90.78	5.293%	$95.585	$95.59	$95.60	$95.60
Purchase #7	$215.54	10.736%	$238.6804	$238.68	$238.70	$238.70
7 purchase totals =	$727.50		$800.7644	$800.77	$800.75	$800.90