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 $62.54   9.841%   $68.6946   $68.69   $68.70   $68.70  
  Purchase #2 $88.77   8.777%   $96.5613   $96.56   $96.55   $96.60  
  Purchase #3 $207.72   12.480%   $233.6435   $233.64   $233.65   $233.60  
  Purchase #4 $80.92   6.636%   $86.2899   $86.29   $86.30   $86.30  
  Purchase #5 $231.52   11.134%   $257.2974   $257.30   $257.30   $257.30  
  Purchase #6 $40.56   10.493%   $44.816   $44.82   $44.80   $44.80  
  Purchase #7 $250.98   4.190%   $261.4961   $261.50   $261.50   $261.50  
  7 purchase totals = $963.01       $1,048.7988   $1,048.80   $1,048.80   $1,048.80