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	$117.50	12.418%	$132.0912	$132.09	$132.10	$132.10
Purchase #2	$76.30	8.140%	$82.5108	$82.51	$82.50	$82.50
Purchase #3	$65.85	10.607%	$72.8347	$72.83	$72.85	$72.80
Purchase #4	$13.67	13.865%	$15.5653	$15.57	$15.55	$15.60
Purchase #5	$215.33	6.715%	$229.7894	$229.79	$229.80	$229.80
Purchase #6	$170.80	8.706%	$185.6698	$185.67	$185.65	$185.70
Purchase #7	$241.50	13.495%	$274.0904	$274.09	$274.10	$274.10
7 purchase totals =	$900.95		$992.5516	$992.55	$992.55	$992.60