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 $88.42   11.451%   $98.545   $98.55   $98.55   $98.50  
  Purchase #2 $235.36   3.569%   $243.76   $243.76   $243.75   $243.80  
  Purchase #3 $193.74   4.201%   $201.879   $201.88   $201.90   $201.90  
  Purchase #4 $42.56   6.233%   $45.2128   $45.21   $45.20   $45.20  
  Purchase #5 $126.38   9.218%   $138.0297   $138.03   $138.05   $138.00  
  Purchase #6 $81.98   4.434%   $85.615   $85.62   $85.60   $85.60  
  Purchase #7 $77.89   8.721%   $84.6828   $84.68   $84.70   $84.70  
  7 purchase totals = $846.33       $897.7243   $897.73   $897.75   $897.70