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	$70.32	12.143%	$78.859	$78.86	$78.85	$78.90
Purchase #2	$18.92	10.263%	$20.8618	$20.86	$20.85	$20.90
Purchase #3	$208.86	9.170%	$228.0125	$228.01	$228.00	$228.00
Purchase #4	$209.99	6.633%	$223.9186	$223.92	$223.90	$223.90
Purchase #5	$201.36	8.733%	$218.9448	$218.94	$218.95	$218.90
Purchase #6	$198.97	8.850%	$216.5788	$216.58	$216.60	$216.60
Purchase #7	$242.92	5.590%	$256.4992	$256.50	$256.50	$256.50
7 purchase totals =	$1,151.34		$1,243.6747	$1,243.67	$1,243.65	$1,243.70