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 $161.45   8.205%   $174.697   $174.70   $174.70   $174.70  
  Purchase #2 $32.78   8.442%   $35.5473   $35.55   $35.55   $35.50  
  Purchase #3 $48.40   9.433%   $52.9656   $52.97   $52.95   $53.00  
  Purchase #4 $155.56   6.247%   $165.2778   $165.28   $165.30   $165.30  
  Purchase #5 $205.88   13.660%   $234.0032   $234.00   $234.00   $234.00  
  Purchase #6 $54.82   6.138%   $58.1849   $58.18   $58.20   $58.20  
  Purchase #7 $6.85   12.629%   $7.7151   $7.72   $7.70   $7.70  
  7 purchase totals = $665.74       $728.3909   $728.40   $728.40   $728.40