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	$112.59	4.709%	$117.8919	$117.89	$117.90	$117.90
Purchase #2	$241.40	4.453%	$252.1495	$252.15	$252.15	$252.10
Purchase #3	$174.31	8.324%	$188.8196	$188.82	$188.80	$188.80
Purchase #4	$210.38	6.874%	$224.8415	$224.84	$224.85	$224.80
Purchase #5	$5.46	6.394%	$5.8091	$5.81	$5.80	$5.80
Purchase #6	$62.90	13.750%	$71.5488	$71.55	$71.55	$71.50
Purchase #7	$136.87	3.716%	$141.9561	$141.96	$141.95	$142.00
7 purchase totals =	$943.91		$1,003.0165	$1,003.02	$1,003.00	$1,002.90