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 $117.63   7.723%   $126.7146   $126.71   $126.70   $126.70  
  Purchase #2 $207.51   5.304%   $218.5163   $218.52   $218.50   $218.50  
  Purchase #3 $30.63   8.323%   $33.1793   $33.18   $33.20   $33.20  
  Purchase #4 $242.43   7.346%   $260.2389   $260.24   $260.25   $260.20  
  Purchase #5 $211.90   9.496%   $232.022   $232.02   $232.00   $232.00  
  Purchase #6 $168.64   10.273%   $185.9644   $185.96   $185.95   $186.00  
  Purchase #7 $18.91   7.184%   $20.2685   $20.27   $20.25   $20.30  
  7 purchase totals = $997.65       $1,076.9040   $1,076.90   $1,076.85   $1,076.90