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 $107.32   6.699%   $114.5094   $114.51   $114.50   $114.50  
  Purchase #2 $42.87   8.803%   $46.6438   $46.64   $46.65   $46.60  
  Purchase #3 $116.81   8.808%   $127.0986   $127.10   $127.10   $127.10  
  Purchase #4 $149.82   10.499%   $165.5496   $165.55   $165.55   $165.50  
  Purchase #5 $32.52   6.481%   $34.6276   $34.63   $34.65   $34.60  
  Purchase #6 $182.25   11.862%   $203.8685   $203.87   $203.85   $203.90  
  Purchase #7 $235.63   6.603%   $251.1886   $251.19   $251.20   $251.20  
  7 purchase totals = $867.22       $943.4861   $943.49   $943.50   $943.40