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 $82.96   3.302%   $85.6993   $85.70   $85.70   $85.70  
  Purchase #2 $238.55   5.621%   $251.9589   $251.96   $251.95   $252.00  
  Purchase #3 $115.33   5.688%   $121.89   $121.89   $121.90   $121.90  
  Purchase #4 $231.72   6.606%   $247.0274   $247.03   $247.05   $247.00  
  Purchase #5 $136.41   12.339%   $153.2416   $153.24   $153.25   $153.20  
  Purchase #6 $122.64   13.872%   $139.6526   $139.65   $139.65   $139.70  
  Purchase #7 $98.54   4.526%   $102.9999   $103.00   $103.00   $103.00  
  7 purchase totals = $1,026.15       $1,102.4697   $1,102.47   $1,102.50   $1,102.50