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 $43.97   10.134%   $48.4259   $48.43   $48.45   $48.40  
  Purchase #2 $173.68   13.318%   $196.8107   $196.81   $196.80   $196.80  
  Purchase #3 $106.96   6.441%   $113.8493   $113.85   $113.85   $113.80  
  Purchase #4 $197.87   13.695%   $224.9683   $224.97   $224.95   $225.00  
  Purchase #5 $202.65   6.743%   $216.3147   $216.31   $216.30   $216.30  
  Purchase #6 $215.35   12.358%   $241.963   $241.96   $241.95   $242.00  
  Purchase #7 $85.47   12.242%   $95.9332   $95.93   $95.95   $95.90  
  7 purchase totals = $1,025.95       $1,138.2651   $1,138.26   $1,138.25   $1,138.20