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 $56.72   5.165%   $59.6496   $59.65   $59.65   $59.60  
  Purchase #2 $171.46   3.589%   $177.6137   $177.61   $177.60   $177.60  
  Purchase #3 $165.56   6.430%   $176.2055   $176.21   $176.20   $176.20  
  Purchase #4 $198.43   13.313%   $224.847   $224.85   $224.85   $224.80  
  Purchase #5 $138.50   4.812%   $145.1646   $145.16   $145.15   $145.20  
  Purchase #6 $240.99   4.586%   $252.0418   $252.04   $252.05   $252.00  
  Purchase #7 $82.80   6.809%   $88.4379   $88.44   $88.45   $88.40  
  7 purchase totals = $1,054.46       $1,123.9601   $1,123.96   $1,123.95   $1,123.80