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 $174.55   11.744%   $195.0492   $195.05   $195.05   $195.00  
  Purchase #2 $225.39   8.451%   $244.4377   $244.44   $244.45   $244.40  
  Purchase #3 $160.50   7.700%   $172.8585   $172.86   $172.85   $172.90  
  Purchase #4 $207.61   7.245%   $222.6513   $222.65   $222.65   $222.70  
  Purchase #5 $153.81   6.696%   $164.1091   $164.11   $164.10   $164.10  
  Purchase #6 $228.31   3.601%   $236.5314   $236.53   $236.55   $236.50  
  Purchase #7 $106.37   6.749%   $113.5489   $113.55   $113.55   $113.50  
  7 purchase totals = $1,256.54       $1,349.1861   $1,349.19   $1,349.20   $1,349.10