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	$127.59	7.815%	$137.5612	$137.56	$137.55	$137.60
Purchase #2	$163.57	6.678%	$174.4932	$174.49	$174.50	$174.50
Purchase #3	$154.38	11.807%	$172.6076	$172.61	$172.60	$172.60
Purchase #4	$113.61	3.362%	$117.4296	$117.43	$117.45	$117.40
Purchase #5	$104.60	4.842%	$109.6647	$109.66	$109.65	$109.70
Purchase #6	$101.36	9.516%	$111.0054	$111.01	$111.00	$111.00
Purchase #7	$232.76	7.616%	$250.487	$250.49	$250.50	$250.50
7 purchase totals =	$997.87		$1,073.2487	$1,073.25	$1,073.25	$1,073.30