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	$217.54	3.730%	$225.6542	$225.65	$225.65	$225.70
Purchase #2	$10.32	11.432%	$11.4998	$11.50	$11.50	$11.50
Purchase #3	$103.80	5.831%	$109.8526	$109.85	$109.85	$109.90
Purchase #4	$86.63	13.240%	$98.0998	$98.10	$98.10	$98.10
Purchase #5	$128.78	6.453%	$137.0902	$137.09	$137.10	$137.10
Purchase #6	$177.97	11.283%	$198.0504	$198.05	$198.05	$198.10
Purchase #7	$96.96	6.745%	$103.5	$103.50	$103.50	$103.50
7 purchase totals =	$822.00		$883.7470	$883.74	$883.75	$883.90