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 $56.59   9.795%   $62.133   $62.13   $62.15   $62.10  
  Purchase #2 $188.77   3.277%   $194.956   $194.96   $194.95   $195.00  
  Purchase #3 $177.25   7.433%   $190.425   $190.43   $190.45   $190.40  
  Purchase #4 $99.61   13.762%   $113.3183   $113.32   $113.30   $113.30  
  Purchase #5 $88.68   6.400%   $94.3555   $94.36   $94.35   $94.40  
  Purchase #6 $53.75   13.822%   $61.1793   $61.18   $61.20   $61.20  
  Purchase #7 $130.98   5.475%   $138.1512   $138.15   $138.15   $138.20  
  7 purchase totals = $795.63       $854.5183   $854.53   $854.55   $854.60