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 $86.91   9.352%   $95.0378   $95.04   $95.05   $95.00  
  Purchase #2 $247.49   10.533%   $273.5581   $273.56   $273.55   $273.60  
  Purchase #3 $151.27   6.691%   $161.3915   $161.39   $161.40   $161.40  
  Purchase #4 $138.92   11.653%   $155.1083   $155.11   $155.10   $155.10  
  Purchase #5 $175.65   9.716%   $192.7162   $192.72   $192.70   $192.70  
  Purchase #6 $50.98   12.238%   $57.2189   $57.22   $57.20   $57.20  
  Purchase #7 $124.54   13.171%   $140.9432   $140.94   $140.95   $140.90  
  7 purchase totals = $975.76       $1,075.9740   $1,075.98   $1,075.95   $1,075.90