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 $68.50   10.859%   $75.9384   $75.94   $75.95   $75.90  
  Purchase #2 $157.62   13.593%   $179.0453   $179.05   $179.05   $179.00  
  Purchase #3 $239.25   12.808%   $269.8931   $269.89   $269.90   $269.90  
  Purchase #4 $218.37   4.422%   $228.0263   $228.03   $228.05   $228.00  
  Purchase #5 $172.34   4.814%   $180.6364   $180.64   $180.65   $180.60  
  Purchase #6 $65.45   13.778%   $74.4677   $74.47   $74.45   $74.50  
  Purchase #7 $123.38   11.525%   $137.5995   $137.60   $137.60   $137.60  
  7 purchase totals = $1,044.91       $1,145.6067   $1,145.62   $1,145.65   $1,145.50