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 $92.65   3.179%   $95.5953   $95.60   $95.60   $95.60  
  Purchase #2 $59.81   5.331%   $62.9985   $63.00   $63.00   $63.00  
  Purchase #3 $219.62   4.129%   $228.6881   $228.69   $228.70   $228.70  
  Purchase #4 $196.60   11.127%   $218.4757   $218.48   $218.50   $218.50  
  Purchase #5 $164.35   11.587%   $183.3932   $183.39   $183.40   $183.40  
  Purchase #6 $42.25   8.137%   $45.6879   $45.69   $45.70   $45.70  
  Purchase #7 $128.85   5.862%   $136.4032   $136.40   $136.40   $136.40  
  7 purchase totals = $904.13       $971.2419   $971.25   $971.30   $971.30