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 $83.42   13.717%   $94.8627   $94.86   $94.85   $94.90  
  Purchase #2 $8.64   4.752%   $9.0506   $9.05   $9.05   $9.10  
  Purchase #3 $39.28   10.225%   $43.2964   $43.30   $43.30   $43.30  
  Purchase #4 $167.47   6.611%   $178.5414   $178.54   $178.55   $178.50  
  Purchase #5 $138.35   12.388%   $155.4888   $155.49   $155.50   $155.50  
  Purchase #6 $199.67   8.354%   $216.3504   $216.35   $216.35   $216.40  
  Purchase #7 $147.25   13.152%   $166.6163   $166.62   $166.60   $166.60  
  7 purchase totals = $784.08       $864.2066   $864.21   $864.20   $864.30