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 $85.73   10.851%   $95.0326   $95.03   $95.05   $95.00  
  Purchase #2 $194.34   4.689%   $203.4526   $203.45   $203.45   $203.50  
  Purchase #3 $32.50   12.158%   $36.4514   $36.45   $36.45   $36.50  
  Purchase #4 $146.56   13.180%   $165.8766   $165.88   $165.90   $165.90  
  Purchase #5 $204.70   6.663%   $218.3392   $218.34   $218.35   $218.30  
  Purchase #6 $233.85   4.632%   $244.6819   $244.68   $244.70   $244.70  
  Purchase #7 $9.38   7.571%   $10.0902   $10.09   $10.10   $10.10  
  7 purchase totals = $907.06       $973.9245   $973.92   $974.00   $974.00