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 $213.73   6.536%   $227.6994   $227.70   $227.70   $227.70  
  Purchase #2 $228.28   3.144%   $235.4571   $235.46   $235.45   $235.50  
  Purchase #3 $59.58   6.185%   $63.265   $63.27   $63.25   $63.30  
  Purchase #4 $250.41   13.224%   $283.5242   $283.52   $283.50   $283.50  
  Purchase #5 $100.64   6.697%   $107.3799   $107.38   $107.40   $107.40  
  Purchase #6 $38.33   8.666%   $41.6517   $41.65   $41.65   $41.70  
  Purchase #7 $65.79   13.650%   $74.7703   $74.77   $74.75   $74.80  
  7 purchase totals = $956.76       $1,033.7476   $1,033.75   $1,033.70   $1,033.90