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 $208.68   11.774%   $233.25   $233.25   $233.25   $233.30  
  Purchase #2 $125.49   7.148%   $134.46   $134.46   $134.45   $134.50  
  Purchase #3 $58.81   9.719%   $64.5257   $64.53   $64.55   $64.50  
  Purchase #4 $216.49   13.257%   $245.1901   $245.19   $245.20   $245.20  
  Purchase #5 $173.86   7.524%   $186.9412   $186.94   $186.95   $186.90  
  Purchase #6 $91.49   5.858%   $96.8495   $96.85   $96.85   $96.80  
  Purchase #7 $195.47   11.574%   $218.0937   $218.09   $218.10   $218.10  
  7 purchase totals = $1,070.29       $1,179.3102   $1,179.31   $1,179.35   $1,179.30