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	$77.73	11.602%	$86.7482	$86.75	$86.75	$86.70
Purchase #2	$170.54	8.816%	$185.5748	$185.57	$185.55	$185.60
Purchase #3	$63.59	13.779%	$72.3521	$72.35	$72.35	$72.40
Purchase #4	$208.82	11.821%	$233.5046	$233.50	$233.50	$233.50
Purchase #5	$162.81	13.249%	$184.3807	$184.38	$184.40	$184.40
Purchase #6	$121.87	4.431%	$127.2701	$127.27	$127.25	$127.30
Purchase #7	$32.35	11.420%	$36.0444	$36.04	$36.05	$36.00
7 purchase totals =	$837.71		$925.8749	$925.86	$925.85	$925.90