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 $113.99   9.835%   $125.2009   $125.20   $125.20   $125.20  
  Purchase #2 $124.93   13.214%   $141.4383   $141.44   $141.45   $141.40  
  Purchase #3 $65.65   12.249%   $73.6915   $73.69   $73.70   $73.70  
  Purchase #4 $195.84   12.629%   $220.5726   $220.57   $220.55   $220.60  
  Purchase #5 $221.27   6.501%   $235.6548   $235.65   $235.65   $235.70  
  Purchase #6 $106.97   12.823%   $120.6868   $120.69   $120.70   $120.70  
  Purchase #7 $122.72   10.834%   $136.0155   $136.02   $136.00   $136.00  
  7 purchase totals = $951.37       $1,053.2604   $1,053.26   $1,053.25   $1,053.30