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	$238.94	7.319%	$256.428	$256.43	$256.45	$256.40
Purchase #2	$49.25	9.280%	$53.8204	$53.82	$53.80	$53.80
Purchase #3	$239.82	3.627%	$248.5183	$248.52	$248.50	$248.50
Purchase #4	$119.43	3.668%	$123.8107	$123.81	$123.80	$123.80
Purchase #5	$174.42	9.216%	$190.4945	$190.49	$190.50	$190.50
Purchase #6	$82.80	6.249%	$87.9742	$87.97	$87.95	$88.00
Purchase #7	$133.38	5.356%	$140.5238	$140.52	$140.50	$140.50
7 purchase totals =	$1,038.04		$1,101.5699	$1,101.56	$1,101.50	$1,101.50