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 $194.57   3.462%   $201.306   $201.31   $201.30   $201.30  
  Purchase #2 $81.30   8.126%   $87.9064   $87.91   $87.90   $87.90  
  Purchase #3 $232.93   3.347%   $240.7262   $240.73   $240.75   $240.70  
  Purchase #4 $14.91   7.658%   $16.0518   $16.05   $16.05   $16.10  
  Purchase #5 $247.54   8.152%   $267.7195   $267.72   $267.70   $267.70  
  Purchase #6 $192.89   7.150%   $206.6816   $206.68   $206.70   $206.70  
  Purchase #7 $206.45   4.533%   $215.8084   $215.81   $215.80   $215.80  
  7 purchase totals = $1,170.59       $1,236.1999   $1,236.21   $1,236.20   $1,236.20