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	$72.35	7.192%	$77.5534	$77.55	$77.55	$77.60
Purchase #2	$161.78	3.502%	$167.4455	$167.45	$167.45	$167.40
Purchase #3	$218.27	3.294%	$225.4598	$225.46	$225.45	$225.50
Purchase #4	$140.89	12.446%	$158.4252	$158.43	$158.45	$158.40
Purchase #5	$48.98	4.652%	$51.2585	$51.26	$51.25	$51.30
Purchase #6	$117.41	5.768%	$124.1822	$124.18	$124.20	$124.20
Purchase #7	$232.85	10.137%	$256.454	$256.45	$256.45	$256.50
7 purchase totals =	$992.53		$1,060.7786	$1,060.78	$1,060.80	$1,060.90