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 $69.81   7.349%   $74.9403   $74.94   $74.95   $74.90  
  Purchase #2 $137.42   4.152%   $143.1257   $143.13   $143.15   $143.10  
  Purchase #3 $182.57   7.566%   $196.3832   $196.38   $196.40   $196.40  
  Purchase #4 $241.75   7.622%   $260.1762   $260.18   $260.20   $260.20  
  Purchase #5 $167.80   7.790%   $180.8716   $180.87   $180.85   $180.90  
  Purchase #6 $159.85   13.516%   $181.4553   $181.46   $181.45   $181.50  
  Purchase #7 $135.82   6.830%   $145.0965   $145.10   $145.10   $145.10  
  7 purchase totals = $1,095.02       $1,182.0488   $1,182.06   $1,182.10   $1,182.10