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 $59.75   5.297%   $62.915   $62.92   $62.90   $62.90  
  Purchase #2 $104.45   3.498%   $108.1037   $108.10   $108.10   $108.10  
  Purchase #3 $218.77   3.697%   $226.8579   $226.86   $226.85   $226.90  
  Purchase #4 $48.94   13.431%   $55.5131   $55.51   $55.50   $55.50  
  Purchase #5 $130.44   10.242%   $143.7997   $143.80   $143.80   $143.80  
  Purchase #6 $49.29   9.436%   $53.941   $53.94   $53.95   $53.90  
  Purchase #7 $202.80   6.600%   $216.1848   $216.18   $216.20   $216.20  
  7 purchase totals = $814.44       $867.3152   $867.31   $867.30   $867.30