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 $34.31   3.223%   $35.4158   $35.42   $35.40   $35.40  
  Purchase #2 $197.94   11.556%   $220.8139   $220.81   $220.80   $220.80  
  Purchase #3 $170.29   5.455%   $179.5793   $179.58   $179.60   $179.60  
  Purchase #4 $89.74   13.236%   $101.618   $101.62   $101.60   $101.60  
  Purchase #5 $213.47   8.422%   $231.4484   $231.45   $231.45   $231.40  
  Purchase #6 $167.74   5.199%   $176.4608   $176.46   $176.45   $176.50  
  Purchase #7 $44.93   11.391%   $50.048   $50.05   $50.05   $50.00  
  7 purchase totals = $918.42       $995.3842   $995.39   $995.35   $995.30