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 $237.32   3.216%   $244.9522   $244.95   $244.95   $245.00  
  Purchase #2 $132.90   7.114%   $142.3545   $142.35   $142.35   $142.40  
  Purchase #3 $240.92   11.652%   $268.992   $268.99   $269.00   $269.00  
  Purchase #4 $94.93   8.560%   $103.056   $103.06   $103.05   $103.10  
  Purchase #5 $171.95   8.581%   $186.705   $186.71   $186.70   $186.70  
  Purchase #6 $51.97   3.390%   $53.7318   $53.73   $53.75   $53.70  
  Purchase #7 $75.26   3.572%   $77.9483   $77.95   $77.95   $77.90  
  7 purchase totals = $1,005.25       $1,077.7398   $1,077.74   $1,077.75   $1,077.80