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 $168.77   8.874%   $183.7466   $183.75   $183.75   $183.70  
  Purchase #2 $104.44   8.440%   $113.2547   $113.25   $113.25   $113.30  
  Purchase #3 $212.86   6.804%   $227.343   $227.34   $227.35   $227.30  
  Purchase #4 $49.58   8.767%   $53.9267   $53.93   $53.95   $53.90  
  Purchase #5 $53.49   7.812%   $57.6686   $57.67   $57.65   $57.70  
  Purchase #6 $202.47   4.360%   $211.2977   $211.30   $211.30   $211.30  
  Purchase #7 $234.83   5.547%   $247.856   $247.86   $247.85   $247.90  
  7 purchase totals = $1,026.44       $1,095.0933   $1,095.10   $1,095.10   $1,095.10