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	$217.50	3.779%	$225.7193	$225.72	$225.70	$225.70
Purchase #2	$173.47	5.727%	$183.4046	$183.40	$183.40	$183.40
Purchase #3	$219.92	9.832%	$241.5425	$241.54	$241.55	$241.50
Purchase #4	$10.47	10.511%	$11.5705	$11.57	$11.55	$11.60
Purchase #5	$189.63	5.476%	$200.0141	$200.01	$200.00	$200.00
Purchase #6	$28.79	10.559%	$31.8299	$31.83	$31.85	$31.80
Purchase #7	$191.86	7.835%	$206.8922	$206.89	$206.90	$206.90
7 purchase totals =	$1,031.64		$1,100.9731	$1,100.96	$1,100.95	$1,100.90