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	$82.90	10.704%	$91.7736	$91.77	$91.75	$91.80
Purchase #2	$146.86	11.791%	$164.1763	$164.18	$164.20	$164.20
Purchase #3	$12.25	11.524%	$13.6617	$13.66	$13.65	$13.70
Purchase #4	$170.60	8.138%	$184.4834	$184.48	$184.50	$184.50
Purchase #5	$198.34	12.778%	$223.6839	$223.68	$223.70	$223.70
Purchase #6	$190.81	4.204%	$198.8317	$198.83	$198.85	$198.80
Purchase #7	$116.36	6.107%	$123.4661	$123.47	$123.45	$123.50
7 purchase totals =	$918.12		$1,000.0767	$1,000.07	$1,000.10	$1,000.20