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 $191.74   7.833%   $206.759   $206.76   $206.75   $206.80  
  Purchase #2 $215.62   8.514%   $233.9779   $233.98   $234.00   $234.00  
  Purchase #3 $58.98   6.208%   $62.6415   $62.64   $62.65   $62.60  
  Purchase #4 $21.86   8.768%   $23.7767   $23.78   $23.80   $23.80  
  Purchase #5 $81.64   5.394%   $86.0437   $86.04   $86.05   $86.00  
  Purchase #6 $223.48   9.844%   $245.4794   $245.48   $245.50   $245.50  
  Purchase #7 $242.81   5.281%   $255.6328   $255.63   $255.65   $255.60  
  7 purchase totals = $1,036.13       $1,114.3110   $1,114.31   $1,114.40   $1,114.30