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 $33.44   4.817%   $35.0508   $35.05   $35.05   $35.10  
  Purchase #2 $224.69   4.557%   $234.9291   $234.93   $234.95   $234.90  
  Purchase #3 $179.96   13.457%   $204.1772   $204.18   $204.20   $204.20  
  Purchase #4 $139.56   3.587%   $144.566   $144.57   $144.55   $144.60  
  Purchase #5 $229.79   11.526%   $256.2756   $256.28   $256.30   $256.30  
  Purchase #6 $107.39   11.171%   $119.3865   $119.39   $119.40   $119.40  
  Purchase #7 $60.28   13.622%   $68.4913   $68.49   $68.50   $68.50  
  7 purchase totals = $975.11       $1,062.8765   $1,062.89   $1,062.95   $1,063.00