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 $59.54   3.660%   $61.7192   $61.72   $61.70   $61.70  
  Purchase #2 $214.77   5.674%   $226.956   $226.96   $226.95   $227.00  
  Purchase #3 $208.29   7.121%   $223.1223   $223.12   $223.10   $223.10  
  Purchase #4 $65.53   3.750%   $67.9874   $67.99   $68.00   $68.00  
  Purchase #5 $240.67   13.735%   $273.726   $273.73   $273.75   $273.70  
  Purchase #6 $66.31   10.689%   $73.3979   $73.40   $73.40   $73.40  
  Purchase #7 $132.56   4.345%   $138.3197   $138.32   $138.30   $138.30  
  7 purchase totals = $987.67       $1,065.2285   $1,065.24   $1,065.20   $1,065.20