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 $108.76   9.627%   $119.2303   $119.23   $119.25   $119.20  
  Purchase #2 $69.61   10.581%   $76.9754   $76.98   $77.00   $77.00  
  Purchase #3 $155.34   11.141%   $172.6464   $172.65   $172.65   $172.60  
  Purchase #4 $235.49   4.286%   $245.5831   $245.58   $245.60   $245.60  
  Purchase #5 $205.84   10.765%   $227.9987   $228.00   $228.00   $228.00  
  Purchase #6 $112.49   5.855%   $119.0763   $119.08   $119.10   $119.10  
  Purchase #7 $212.63   10.868%   $235.7386   $235.74   $235.75   $235.70  
  7 purchase totals = $1,100.16       $1,197.2488   $1,197.26   $1,197.35   $1,197.20