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	$148.42	4.813%	$155.5635	$155.56	$155.55	$155.60
Purchase #2	$178.82	3.256%	$184.6424	$184.64	$184.65	$184.60
Purchase #3	$71.47	12.221%	$80.2043	$80.20	$80.20	$80.20
Purchase #4	$24.92	11.767%	$27.8523	$27.85	$27.85	$27.90
Purchase #5	$143.48	6.351%	$152.5924	$152.59	$152.60	$152.60
Purchase #6	$185.48	7.263%	$198.9514	$198.95	$198.95	$199.00
Purchase #7	$196.36	8.732%	$213.5062	$213.51	$213.50	$213.50
7 purchase totals =	$948.95		$1,013.3125	$1,013.30	$1,013.30	$1,013.40