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 $57.59   7.526%   $61.9242   $61.92   $61.90   $61.90  
  Purchase #2 $224.73   11.379%   $250.302   $250.30   $250.30   $250.30  
  Purchase #3 $64.77   5.799%   $68.526   $68.53   $68.55   $68.50  
  Purchase #4 $144.97   12.170%   $162.6128   $162.61   $162.60   $162.60  
  Purchase #5 $104.33   4.205%   $108.7171   $108.72   $108.70   $108.70  
  Purchase #6 $35.73   10.753%   $39.572   $39.57   $39.55   $39.60  
  Purchase #7 $56.29   7.568%   $60.55   $60.55   $60.55   $60.60  
  7 purchase totals = $688.41       $752.2041   $752.20   $752.15   $752.20