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	$101.85	7.578%	$109.5682	$109.57	$109.55	$109.60
Purchase #2	$109.74	7.168%	$117.6062	$117.61	$117.60	$117.60
Purchase #3	$86.96	7.384%	$93.3811	$93.38	$93.40	$93.40
Purchase #4	$180.48	5.532%	$190.4642	$190.46	$190.45	$190.50
Purchase #5	$133.51	6.767%	$142.5446	$142.54	$142.55	$142.50
Purchase #6	$214.38	10.750%	$237.4259	$237.43	$237.45	$237.40
Purchase #7	$166.75	13.838%	$189.8249	$189.82	$189.80	$189.80
7 purchase totals =	$993.67		$1,080.8151	$1,080.81	$1,080.80	$1,080.80