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 $214.86   13.598%   $244.0767   $244.08   $244.10   $244.10  
  Purchase #2 $127.92   13.845%   $145.6305   $145.63   $145.65   $145.60  
  Purchase #3 $196.29   4.211%   $204.5558   $204.56   $204.55   $204.60  
  Purchase #4 $26.45   6.799%   $28.2483   $28.25   $28.25   $28.20  
  Purchase #5 $52.91   10.554%   $58.4941   $58.49   $58.50   $58.50  
  Purchase #6 $188.80   4.368%   $197.0468   $197.05   $197.05   $197.00  
  Purchase #7 $121.90   13.211%   $138.0042   $138.00   $138.00   $138.00  
  7 purchase totals = $929.13       $1,016.0564   $1,016.06   $1,016.10   $1,016.00