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 $59.83   6.753%   $63.8703   $63.87   $63.85   $63.90  
  Purchase #2 $235.27   5.411%   $248.0005   $248.00   $248.00   $248.00  
  Purchase #3 $169.78   3.747%   $176.1417   $176.14   $176.15   $176.10  
  Purchase #4 $117.92   11.768%   $131.7968   $131.80   $131.80   $131.80  
  Purchase #5 $216.30   9.442%   $236.723   $236.72   $236.70   $236.70  
  Purchase #6 $75.91   4.209%   $79.1051   $79.11   $79.10   $79.10  
  Purchase #7 $25.42   8.472%   $27.5736   $27.57   $27.55   $27.60  
  7 purchase totals = $900.43       $963.2110   $963.21   $963.15   $963.20