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 $168.61   8.330%   $182.6552   $182.66   $182.65   $182.70  
  Purchase #2 $198.50   9.292%   $216.9446   $216.94   $216.95   $216.90  
  Purchase #3 $25.44   12.170%   $28.536   $28.54   $28.55   $28.50  
  Purchase #4 $97.85   8.172%   $105.8463   $105.85   $105.85   $105.80  
  Purchase #5 $226.70   6.839%   $242.204   $242.20   $242.20   $242.20  
  Purchase #6 $233.31   5.152%   $245.3301   $245.33   $245.35   $245.30  
  Purchase #7 $226.53   6.818%   $241.9748   $241.97   $241.95   $242.00  
  7 purchase totals = $1,176.94       $1,263.4910   $1,263.49   $1,263.50   $1,263.40