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 $102.69   7.311%   $110.1977   $110.20   $110.20   $110.20  
  Purchase #2 $183.33   4.515%   $191.6073   $191.61   $191.60   $191.60  
  Purchase #3 $245.27   12.120%   $274.9967   $275.00   $275.00   $275.00  
  Purchase #4 $159.29   7.381%   $171.0472   $171.05   $171.05   $171.00  
  Purchase #5 $86.60   4.595%   $90.5793   $90.58   $90.60   $90.60  
  Purchase #6 $182.78   10.812%   $202.5422   $202.54   $202.55   $202.50  
  Purchase #7 $68.74   4.828%   $72.0588   $72.06   $72.05   $72.10  
  7 purchase totals = $1,028.70       $1,113.0292   $1,113.04   $1,113.05   $1,113.00