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 $211.50   10.262%   $233.2041   $233.20   $233.20   $233.20  
  Purchase #2 $25.57   4.461%   $26.7107   $26.71   $26.70   $26.70  
  Purchase #3 $61.62   7.143%   $66.0215   $66.02   $66.00   $66.00  
  Purchase #4 $38.79   13.140%   $43.887   $43.89   $43.90   $43.90  
  Purchase #5 $176.86   9.223%   $193.1718   $193.17   $193.15   $193.20  
  Purchase #6 $149.75   13.785%   $170.393   $170.39   $170.40   $170.40  
  Purchase #7 $194.75   8.786%   $211.8607   $211.86   $211.85   $211.90  
  7 purchase totals = $858.84       $945.2488   $945.24   $945.20   $945.30