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	$199.80	10.837%	$221.4523	$221.45	$221.45	$221.50
Purchase #2	$194.82	10.294%	$214.8748	$214.87	$214.85	$214.90
Purchase #3	$89.78	9.686%	$98.4761	$98.48	$98.50	$98.50
Purchase #4	$205.90	5.809%	$217.8607	$217.86	$217.85	$217.90
Purchase #5	$24.86	9.312%	$27.175	$27.18	$27.20	$27.20
Purchase #6	$231.51	4.764%	$242.5391	$242.54	$242.55	$242.50
Purchase #7	$58.52	10.160%	$64.4656	$64.47	$64.45	$64.50
7 purchase totals =	$1,005.19		$1,086.8436	$1,086.85	$1,086.85	$1,087.00