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 $148.79   5.457%   $156.9095   $156.91   $156.90   $156.90  
  Purchase #2 $16.72   5.541%   $17.6465   $17.65   $17.65   $17.60  
  Purchase #3 $61.66   5.347%   $64.957   $64.96   $64.95   $65.00  
  Purchase #4 $162.53   11.372%   $181.0129   $181.01   $181.00   $181.00  
  Purchase #5 $186.41   5.461%   $196.5899   $196.59   $196.60   $196.60  
  Purchase #6 $110.62   10.346%   $122.0647   $122.06   $122.05   $122.10  
  Purchase #7 $165.32   5.619%   $174.6093   $174.61   $174.60   $174.60  
  7 purchase totals = $852.05       $913.7898   $913.79   $913.75   $913.80