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	$161.57	6.867%	$172.665	$172.67	$172.65	$172.70
Purchase #2	$224.89	12.660%	$253.3611	$253.36	$253.35	$253.40
Purchase #3	$120.31	10.163%	$132.5371	$132.54	$132.55	$132.50
Purchase #4	$144.66	13.718%	$164.5045	$164.50	$164.50	$164.50
Purchase #5	$80.82	12.324%	$90.7803	$90.78	$90.80	$90.80
Purchase #6	$111.47	7.419%	$119.74	$119.74	$119.75	$119.70
Purchase #7	$80.74	12.452%	$90.7937	$90.79	$90.80	$90.80
7 purchase totals =	$924.46		$1,024.3817	$1,024.38	$1,024.40	$1,024.40