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 $103.97   9.661%   $114.0145   $114.01   $114.00   $114.00  
  Purchase #2 $207.37   6.795%   $221.4608   $221.46   $221.45   $221.50  
  Purchase #3 $52.98   6.822%   $56.5943   $56.59   $56.60   $56.60  
  Purchase #4 $62.36   11.145%   $69.31   $69.31   $69.30   $69.30  
  Purchase #5 $101.70   8.802%   $110.6516   $110.65   $110.65   $110.70  
  Purchase #6 $123.81   10.116%   $136.3346   $136.33   $136.35   $136.30  
  Purchase #7 $224.95   8.473%   $244.01   $244.01   $244.00   $244.00  
  7 purchase totals = $877.14       $952.3758   $952.36   $952.35   $952.40