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 $216.27   3.855%   $224.6072   $224.61   $224.60   $224.60  
  Purchase #2 $214.64   8.387%   $232.6419   $232.64   $232.65   $232.60  
  Purchase #3 $6.97   3.502%   $7.2141   $7.21   $7.20   $7.20  
  Purchase #4 $80.85   12.751%   $91.1592   $91.16   $91.15   $91.20  
  Purchase #5 $249.58   11.150%   $277.4082   $277.41   $277.40   $277.40  
  Purchase #6 $182.33   4.391%   $190.3361   $190.34   $190.35   $190.30  
  Purchase #7 $22.99   8.566%   $24.9593   $24.96   $24.95   $25.00  
  7 purchase totals = $973.63       $1,048.3260   $1,048.33   $1,048.30   $1,048.30