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	$87.85	7.693%	$94.6083	$94.61	$94.60	$94.60
Purchase #2	$160.51	3.867%	$166.7169	$166.72	$166.70	$166.70
Purchase #3	$78.92	11.140%	$87.7117	$87.71	$87.70	$87.70
Purchase #4	$190.51	3.220%	$196.6444	$196.64	$196.65	$196.60
Purchase #5	$144.25	10.238%	$159.0183	$159.02	$159.00	$159.00
Purchase #6	$116.33	6.140%	$123.4727	$123.47	$123.45	$123.50
Purchase #7	$16.91	11.743%	$18.8957	$18.90	$18.90	$18.90
7 purchase totals =	$795.28		$847.0680	$847.07	$847.00	$847.00