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 $86.63   11.602%   $96.6808   $96.68   $96.70   $96.70  
  Purchase #2 $206.82   5.840%   $218.8983   $218.90   $218.90   $218.90  
  Purchase #3 $234.30   4.753%   $245.4363   $245.44   $245.45   $245.40  
  Purchase #4 $68.86   3.153%   $71.0312   $71.03   $71.05   $71.00  
  Purchase #5 $186.92   3.567%   $193.5874   $193.59   $193.60   $193.60  
  Purchase #6 $91.64   6.504%   $97.6003   $97.60   $97.60   $97.60  
  Purchase #7 $39.60   11.676%   $44.2237   $44.22   $44.20   $44.20  
  7 purchase totals = $914.77       $967.4580   $967.46   $967.50   $967.40