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 $102.58   8.162%   $110.9526   $110.95   $110.95   $111.00  
  Purchase #2 $156.27   13.222%   $176.932   $176.93   $176.95   $176.90  
  Purchase #3 $192.73   5.675%   $203.6674   $203.67   $203.65   $203.70  
  Purchase #4 $216.43   5.805%   $228.9938   $228.99   $229.00   $229.00  
  Purchase #5 $77.37   6.151%   $82.129   $82.13   $82.15   $82.10  
  Purchase #6 $108.92   3.806%   $113.0655   $113.07   $113.05   $113.10  
  Purchase #7 $87.86   13.527%   $99.7448   $99.74   $99.75   $99.70  
  7 purchase totals = $942.16       $1,015.4851   $1,015.48   $1,015.50   $1,015.50