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 $59.88   4.720%   $62.7063   $62.71   $62.70   $62.70  
  Purchase #2 $117.57   6.843%   $125.6153   $125.62   $125.60   $125.60  
  Purchase #3 $213.53   11.325%   $237.7123   $237.71   $237.70   $237.70  
  Purchase #4 $177.94   3.105%   $183.465   $183.47   $183.45   $183.50  
  Purchase #5 $112.52   6.874%   $120.2546   $120.25   $120.25   $120.30  
  Purchase #6 $119.67   6.556%   $127.5156   $127.52   $127.50   $127.50  
  Purchase #7 $219.42   7.771%   $236.4711   $236.47   $236.45   $236.50  
  7 purchase totals = $1,020.53       $1,093.7402   $1,093.75   $1,093.65   $1,093.80