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 $41.87   11.420%   $46.6516   $46.65   $46.65   $46.70  
  Purchase #2 $35.84   10.766%   $39.6985   $39.70   $39.70   $39.70  
  Purchase #3 $31.58   3.228%   $32.5994   $32.60   $32.60   $32.60  
  Purchase #4 $180.32   7.547%   $193.9288   $193.93   $193.95   $193.90  
  Purchase #5 $98.64   6.435%   $104.9875   $104.99   $105.00   $105.00  
  Purchase #6 $154.99   13.823%   $176.4143   $176.41   $176.40   $176.40  
  Purchase #7 $101.72   7.802%   $109.6562   $109.66   $109.65   $109.70  
  7 purchase totals = $644.96       $703.9363   $703.94   $703.95   $704.00