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 $195.65   3.656%   $202.803   $202.80   $202.80   $202.80  
  Purchase #2 $84.47   9.118%   $92.172   $92.17   $92.15   $92.20  
  Purchase #3 $220.87   7.251%   $236.8853   $236.89   $236.90   $236.90  
  Purchase #4 $215.44   11.785%   $240.8296   $240.83   $240.85   $240.80  
  Purchase #5 $171.57   11.109%   $190.6297   $190.63   $190.65   $190.60  
  Purchase #6 $38.31   8.727%   $41.6533   $41.65   $41.65   $41.70  
  Purchase #7 $45.92   10.213%   $50.6098   $50.61   $50.60   $50.60  
  7 purchase totals = $972.23       $1,055.5827   $1,055.58   $1,055.60   $1,055.60