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 $62.56   8.732%   $68.0227   $68.02   $68.00   $68.00  
  Purchase #2 $217.65   10.156%   $239.7545   $239.75   $239.75   $239.80  
  Purchase #3 $222.60   8.551%   $241.6345   $241.63   $241.65   $241.60  
  Purchase #4 $234.32   4.847%   $245.6775   $245.68   $245.70   $245.70  
  Purchase #5 $52.80   13.579%   $59.9697   $59.97   $59.95   $60.00  
  Purchase #6 $91.96   5.305%   $96.8385   $96.84   $96.85   $96.80  
  Purchase #7 $132.80   6.837%   $141.8795   $141.88   $141.90   $141.90  
  7 purchase totals = $1,014.69       $1,093.7769   $1,093.77   $1,093.80   $1,093.80