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 $184.62   5.164%   $194.1538   $194.15   $194.15   $194.20  
  Purchase #2 $179.81   10.394%   $198.4995   $198.50   $198.50   $198.50  
  Purchase #3 $32.56   6.436%   $34.6556   $34.66   $34.65   $34.70  
  Purchase #4 $202.65   12.386%   $227.7502   $227.75   $227.75   $227.80  
  Purchase #5 $81.59   4.378%   $85.162   $85.16   $85.15   $85.20  
  Purchase #6 $148.91   4.544%   $155.6765   $155.68   $155.70   $155.70  
  Purchase #7 $190.42   6.222%   $202.2679   $202.27   $202.25   $202.30  
  7 purchase totals = $1,020.56       $1,098.1655   $1,098.17   $1,098.15   $1,098.40