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 $85.32   13.334%   $96.6966   $96.70   $96.70   $96.70  
  Purchase #2 $160.46   5.782%   $169.7378   $169.74   $169.75   $169.70  
  Purchase #3 $232.70   8.229%   $251.8489   $251.85   $251.85   $251.80  
  Purchase #4 $225.46   9.790%   $247.5325   $247.53   $247.55   $247.50  
  Purchase #5 $172.61   8.624%   $187.4959   $187.50   $187.50   $187.50  
  Purchase #6 $161.89   13.473%   $183.7014   $183.70   $183.70   $183.70  
  Purchase #7 $247.68   4.396%   $258.568   $258.57   $258.55   $258.60  
  7 purchase totals = $1,286.12       $1,395.5811   $1,395.59   $1,395.60   $1,395.50