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 $195.71   9.259%   $213.8308   $213.83   $213.85   $213.80  
  Purchase #2 $216.81   8.468%   $235.1695   $235.17   $235.15   $235.20  
  Purchase #3 $29.45   12.529%   $33.1398   $33.14   $33.15   $33.10  
  Purchase #4 $228.61   8.133%   $247.2029   $247.20   $247.20   $247.20  
  Purchase #5 $24.73   7.779%   $26.6537   $26.65   $26.65   $26.70  
  Purchase #6 $134.32   4.591%   $140.4866   $140.49   $140.50   $140.50  
  Purchase #7 $165.50   11.747%   $184.9413   $184.94   $184.95   $184.90  
  7 purchase totals = $995.13       $1,081.4246   $1,081.42   $1,081.45   $1,081.40