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 $32.86   6.717%   $35.0672   $35.07   $35.05   $35.10  
  Purchase #2 $239.89   10.466%   $264.9969   $265.00   $265.00   $265.00  
  Purchase #3 $93.74   9.195%   $102.3594   $102.36   $102.35   $102.40  
  Purchase #4 $19.98   8.444%   $21.6671   $21.67   $21.65   $21.70  
  Purchase #5 $211.79   7.871%   $228.46   $228.46   $228.45   $228.50  
  Purchase #6 $149.57   5.415%   $157.6692   $157.67   $157.65   $157.70  
  Purchase #7 $145.95   5.798%   $154.4122   $154.41   $154.40   $154.40  
  7 purchase totals = $893.78       $964.6320   $964.64   $964.55   $964.80