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 $146.95   3.803%   $152.5385   $152.54   $152.55   $152.50  
  Purchase #2 $193.94   3.443%   $200.6174   $200.62   $200.60   $200.60  
  Purchase #3 $249.40   10.306%   $275.1032   $275.10   $275.10   $275.10  
  Purchase #4 $46.29   7.723%   $49.865   $49.87   $49.85   $49.90  
  Purchase #5 $124.91   4.353%   $130.3473   $130.35   $130.35   $130.30  
  Purchase #6 $175.89   3.691%   $182.3821   $182.38   $182.40   $182.40  
  Purchase #7 $181.74   12.676%   $204.7774   $204.78   $204.80   $204.80  
  7 purchase totals = $1,119.12       $1,195.6309   $1,195.64   $1,195.65   $1,195.60