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 $213.79   5.293%   $225.1059   $225.11   $225.10   $225.10  
  Purchase #2 $67.55   12.133%   $75.7458   $75.75   $75.75   $75.70  
  Purchase #3 $32.77   9.337%   $35.8297   $35.83   $35.85   $35.80  
  Purchase #4 $223.99   8.713%   $243.5062   $243.51   $243.50   $243.50  
  Purchase #5 $28.32   5.732%   $29.9433   $29.94   $29.95   $29.90  
  Purchase #6 $179.34   10.387%   $197.968   $197.97   $197.95   $198.00  
  Purchase #7 $200.51   13.210%   $226.9974   $227.00   $227.00   $227.00  
  7 purchase totals = $946.27       $1,035.0963   $1,035.11   $1,035.10   $1,035.00