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 $87.51   9.631%   $95.9381   $95.94   $95.95   $95.90  
  Purchase #2 $246.94   10.836%   $273.6984   $273.70   $273.70   $273.70  
  Purchase #3 $221.99   9.758%   $243.6518   $243.65   $243.65   $243.70  
  Purchase #4 $47.44   5.248%   $49.9297   $49.93   $49.95   $49.90  
  Purchase #5 $85.85   6.431%   $91.371   $91.37   $91.35   $91.40  
  Purchase #6 $195.43   13.422%   $221.6606   $221.66   $221.65   $221.70  
  Purchase #7 $188.75   9.420%   $206.5303   $206.53   $206.55   $206.50  
  7 purchase totals = $1,073.91       $1,182.7799   $1,182.78   $1,182.80   $1,182.80