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 $71.28   6.649%   $76.0194   $76.02   $76.00   $76.00  
  Purchase #2 $196.70   11.167%   $218.6655   $218.67   $218.65   $218.70  
  Purchase #3 $142.65   13.863%   $162.4256   $162.43   $162.45   $162.40  
  Purchase #4 $191.76   6.411%   $204.0537   $204.05   $204.05   $204.10  
  Purchase #5 $117.59   12.703%   $132.5275   $132.53   $132.55   $132.50  
  Purchase #6 $240.68   11.641%   $268.6976   $268.70   $268.70   $268.70  
  Purchase #7 $224.83   3.158%   $231.9301   $231.93   $231.95   $231.90  
  7 purchase totals = $1,185.49       $1,294.3194   $1,294.33   $1,294.35   $1,294.30