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	$176.84	13.346%	$200.4411	$200.44	$200.45	$200.40
Purchase #2	$154.75	13.412%	$175.5051	$175.51	$175.50	$175.50
Purchase #3	$29.97	8.732%	$32.587	$32.59	$32.60	$32.60
Purchase #4	$45.81	10.234%	$50.4982	$50.50	$50.50	$50.50
Purchase #5	$207.83	7.491%	$223.3985	$223.40	$223.40	$223.40
Purchase #6	$63.33	4.753%	$66.3401	$66.34	$66.35	$66.30
Purchase #7	$101.78	10.506%	$112.473	$112.47	$112.45	$112.50
7 purchase totals =	$780.31		$861.2430	$861.25	$861.25	$861.20