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 $212.37   10.611%   $234.9046   $234.90   $234.90   $234.90  
  Purchase #2 $232.34   9.126%   $253.5433   $253.54   $253.55   $253.50  
  Purchase #3 $31.33   10.513%   $34.6237   $34.62   $34.60   $34.60  
  Purchase #4 $71.77   12.637%   $80.8396   $80.84   $80.85   $80.80  
  Purchase #5 $50.81   13.225%   $57.5296   $57.53   $57.55   $57.50  
  Purchase #6 $133.85   12.635%   $150.7619   $150.76   $150.75   $150.80  
  Purchase #7 $193.87   9.413%   $212.119   $212.12   $212.10   $212.10  
  7 purchase totals = $926.34       $1,024.3217   $1,024.31   $1,024.30   $1,024.20