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 $183.34   10.165%   $201.9765   $201.98   $202.00   $202.00  
  Purchase #2 $230.92   13.384%   $261.8263   $261.83   $261.85   $261.80  
  Purchase #3 $200.34   12.113%   $224.6072   $224.61   $224.60   $224.60  
  Purchase #4 $213.74   3.444%   $221.1012   $221.10   $221.10   $221.10  
  Purchase #5 $42.64   8.831%   $46.4055   $46.41   $46.40   $46.40  
  Purchase #6 $8.38   11.355%   $9.3315   $9.33   $9.35   $9.30  
  Purchase #7 $133.66   13.758%   $152.0489   $152.05   $152.05   $152.00  
  7 purchase totals = $1,013.02       $1,117.2971   $1,117.31   $1,117.35   $1,117.20