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 $119.69   4.816%   $125.4543   $125.45   $125.45   $125.50  
  Purchase #2 $49.39   6.453%   $52.5771   $52.58   $52.60   $52.60  
  Purchase #3 $215.38   6.517%   $229.4163   $229.42   $229.40   $229.40  
  Purchase #4 $87.97   13.564%   $99.9023   $99.90   $99.90   $99.90  
  Purchase #5 $243.79   13.335%   $276.2994   $276.30   $276.30   $276.30  
  Purchase #6 $180.52   5.409%   $190.2843   $190.28   $190.30   $190.30  
  Purchase #7 $178.63   4.867%   $187.3239   $187.32   $187.30   $187.30  
  7 purchase totals = $1,075.37       $1,161.2576   $1,161.25   $1,161.25   $1,161.30