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 $56.99   10.829%   $63.1614   $63.16   $63.15   $63.20  
  Purchase #2 $168.79   7.487%   $181.4273   $181.43   $181.45   $181.40  
  Purchase #3 $230.83   6.719%   $246.3395   $246.34   $246.35   $246.30  
  Purchase #4 $234.38   4.554%   $245.0537   $245.05   $245.05   $245.10  
  Purchase #5 $218.95   6.514%   $233.2124   $233.21   $233.20   $233.20  
  Purchase #6 $150.79   5.855%   $159.6188   $159.62   $159.60   $159.60  
  Purchase #7 $95.87   7.850%   $103.3958   $103.40   $103.40   $103.40  
  7 purchase totals = $1,156.60       $1,232.2089   $1,232.21   $1,232.20   $1,232.20