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	$46.86	9.551%	$51.3356	$51.34	$51.35	$51.30
Purchase #2	$128.87	11.385%	$143.5418	$143.54	$143.55	$143.50
Purchase #3	$246.35	5.514%	$259.9337	$259.93	$259.95	$259.90
Purchase #4	$54.26	9.337%	$59.3263	$59.33	$59.35	$59.30
Purchase #5	$247.93	3.121%	$255.6679	$255.67	$255.65	$255.70
Purchase #6	$215.50	11.679%	$240.6682	$240.67	$240.65	$240.70
Purchase #7	$141.31	10.405%	$156.0133	$156.01	$156.00	$156.00
7 purchase totals =	$1,081.08		$1,166.4868	$1,166.49	$1,166.50	$1,166.40