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 $58.76   10.686%   $65.0391   $65.04   $65.05   $65.00  
  Purchase #2 $10.73   12.217%   $12.0409   $12.04   $12.05   $12.00  
  Purchase #3 $49.82   9.600%   $54.6027   $54.60   $54.60   $54.60  
  Purchase #4 $71.27   8.485%   $77.3173   $77.32   $77.30   $77.30  
  Purchase #5 $200.70   13.142%   $227.076   $227.08   $227.10   $227.10  
  Purchase #6 $78.45   6.362%   $83.441   $83.44   $83.45   $83.40  
  Purchase #7 $165.33   11.698%   $184.6703   $184.67   $184.65   $184.70  
  7 purchase totals = $635.06       $704.1873   $704.19   $704.20   $704.10