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 $181.72   7.270%   $194.931   $194.93   $194.95   $194.90  
  Purchase #2 $84.69   13.266%   $95.925   $95.93   $95.95   $95.90  
  Purchase #3 $163.29   13.745%   $185.7342   $185.73   $185.75   $185.70  
  Purchase #4 $218.73   10.739%   $242.2194   $242.22   $242.20   $242.20  
  Purchase #5 $186.62   9.238%   $203.86   $203.86   $203.85   $203.90  
  Purchase #6 $82.54   7.786%   $88.9666   $88.97   $88.95   $89.00  
  Purchase #7 $123.96   8.710%   $134.7569   $134.76   $134.75   $134.80  
  7 purchase totals = $1,041.55       $1,146.3931   $1,146.40   $1,146.40   $1,146.40