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 $229.55   11.110%   $255.053   $255.05   $255.05   $255.10  
  Purchase #2 $76.68   3.776%   $79.5754   $79.58   $79.60   $79.60  
  Purchase #3 $175.28   10.244%   $193.2357   $193.24   $193.25   $193.20  
  Purchase #4 $119.77   4.819%   $125.5417   $125.54   $125.55   $125.50  
  Purchase #5 $205.49   7.452%   $220.8031   $220.80   $220.80   $220.80  
  Purchase #6 $205.88   9.385%   $225.2018   $225.20   $225.20   $225.20  
  Purchase #7 $209.84   8.219%   $227.0867   $227.09   $227.10   $227.10  
  7 purchase totals = $1,222.49       $1,326.4974   $1,326.50   $1,326.55   $1,326.50