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 $60.86   4.629%   $63.6772   $63.68   $63.70   $63.70  
  Purchase #2 $138.36   8.684%   $150.3752   $150.38   $150.40   $150.40  
  Purchase #3 $24.70   5.148%   $25.9716   $25.97   $25.95   $26.00  
  Purchase #4 $27.68   6.347%   $29.4368   $29.44   $29.45   $29.40  
  Purchase #5 $42.57   8.586%   $46.2251   $46.23   $46.25   $46.20  
  Purchase #6 $212.25   3.500%   $219.6788   $219.68   $219.70   $219.70  
  Purchase #7 $147.48   10.707%   $163.2707   $163.27   $163.25   $163.30  
  7 purchase totals = $653.90       $698.6354   $698.65   $698.70   $698.70