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 $41.66   7.864%   $44.9361   $44.94   $44.95   $44.90  
  Purchase #2 $210.95   11.194%   $234.5637   $234.56   $234.55   $234.60  
  Purchase #3 $239.43   7.720%   $257.914   $257.91   $257.90   $257.90  
  Purchase #4 $87.95   10.212%   $96.9315   $96.93   $96.95   $96.90  
  Purchase #5 $188.90   7.371%   $202.8238   $202.82   $202.80   $202.80  
  Purchase #6 $175.33   10.724%   $194.1324   $194.13   $194.15   $194.10  
  Purchase #7 $83.89   11.325%   $93.3905   $93.39   $93.40   $93.40  
  7 purchase totals = $1,028.11       $1,124.6920   $1,124.68   $1,124.70   $1,124.60