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 $68.95   11.584%   $76.9372   $76.94   $76.95   $76.90  
  Purchase #2 $212.91   6.559%   $226.8748   $226.87   $226.85   $226.90  
  Purchase #3 $159.25   8.121%   $172.1827   $172.18   $172.20   $172.20  
  Purchase #4 $80.26   8.388%   $86.9922   $86.99   $87.00   $87.00  
  Purchase #5 $77.48   9.720%   $85.0111   $85.01   $85.00   $85.00  
  Purchase #6 $51.92   11.571%   $57.9277   $57.93   $57.95   $57.90  
  Purchase #7 $57.47   9.761%   $63.0796   $63.08   $63.10   $63.10  
  7 purchase totals = $708.24       $769.0053   $769.00   $769.05   $769.00