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 $59.95   8.735%   $65.1866   $65.19   $65.20   $65.20  
  Purchase #2 $157.44   11.338%   $175.2905   $175.29   $175.30   $175.30  
  Purchase #3 $222.43   4.232%   $231.8432   $231.84   $231.85   $231.80  
  Purchase #4 $137.53   8.688%   $149.4786   $149.48   $149.50   $149.50  
  Purchase #5 $153.91   4.591%   $160.976   $160.98   $161.00   $161.00  
  Purchase #6 $234.49   7.500%   $252.0768   $252.08   $252.10   $252.10  
  Purchase #7 $82.82   12.266%   $92.9787   $92.98   $93.00   $93.00  
  7 purchase totals = $1,048.57       $1,127.8304   $1,127.84   $1,127.95   $1,127.90