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 $210.61   12.625%   $237.1995   $237.20   $237.20   $237.20  
  Purchase #2 $71.89   9.735%   $78.8885   $78.89   $78.90   $78.90  
  Purchase #3 $145.35   6.644%   $155.0071   $155.01   $155.00   $155.00  
  Purchase #4 $176.41   12.540%   $198.5318   $198.53   $198.55   $198.50  
  Purchase #5 $58.80   10.694%   $65.0881   $65.09   $65.10   $65.10  
  Purchase #6 $237.91   5.395%   $250.7452   $250.75   $250.75   $250.70  
  Purchase #7 $43.97   9.128%   $47.9836   $47.98   $48.00   $48.00  
  7 purchase totals = $944.94       $1,033.4438   $1,033.45   $1,033.50   $1,033.40