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	$211.90	4.786%	$222.0415	$222.04	$222.05	$222.00
Purchase #2	$215.80	8.776%	$234.7386	$234.74	$234.75	$234.70
Purchase #3	$38.80	3.154%	$40.0238	$40.02	$40.00	$40.00
Purchase #4	$37.67	12.213%	$42.2706	$42.27	$42.25	$42.30
Purchase #5	$28.78	12.671%	$32.4267	$32.43	$32.45	$32.40
Purchase #6	$242.80	10.816%	$269.0612	$269.06	$269.05	$269.10
Purchase #7	$14.87	7.473%	$15.9812	$15.98	$16.00	$16.00
7 purchase totals =	$790.62		$856.5436	$856.54	$856.55	$856.50