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 $190.96   10.601%   $211.2037   $211.20   $211.20   $211.20  
  Purchase #2 $85.72   7.632%   $92.2622   $92.26   $92.25   $92.30  
  Purchase #3 $191.98   7.788%   $206.9314   $206.93   $206.95   $206.90  
  Purchase #4 $216.49   3.857%   $224.84   $224.84   $224.85   $224.80  
  Purchase #5 $130.44   4.779%   $136.6737   $136.67   $136.65   $136.70  
  Purchase #6 $48.69   8.573%   $52.8642   $52.86   $52.85   $52.90  
  Purchase #7 $134.39   12.742%   $151.514   $151.51   $151.50   $151.50  
  7 purchase totals = $998.67       $1,076.2892   $1,076.27   $1,076.25   $1,076.30