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	$136.50	12.577%	$153.6676	$153.67	$153.65	$153.70
Purchase #2	$37.68	13.833%	$42.8923	$42.89	$42.90	$42.90
Purchase #3	$93.71	6.640%	$99.9323	$99.93	$99.95	$99.90
Purchase #4	$237.60	6.403%	$252.8135	$252.81	$252.80	$252.80
Purchase #5	$41.36	3.571%	$42.837	$42.84	$42.85	$42.80
Purchase #6	$37.82	4.617%	$39.5661	$39.57	$39.55	$39.60
Purchase #7	$75.85	6.693%	$80.9266	$80.93	$80.95	$80.90
7 purchase totals =	$660.52		$712.6354	$712.64	$712.65	$712.60