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 $200.85   3.541%   $207.9621   $207.96   $207.95   $208.00  
  Purchase #2 $232.72   11.863%   $260.3276   $260.33   $260.35   $260.30  
  Purchase #3 $27.31   6.416%   $29.0622   $29.06   $29.05   $29.10  
  Purchase #4 $206.50   13.205%   $233.7683   $233.77   $233.75   $233.80  
  Purchase #5 $47.76   11.421%   $53.2147   $53.21   $53.20   $53.20  
  Purchase #6 $194.62   10.307%   $214.6795   $214.68   $214.70   $214.70  
  Purchase #7 $35.32   10.462%   $39.0152   $39.02   $39.00   $39.00  
  7 purchase totals = $945.08       $1,038.0296   $1,038.03   $1,038.00   $1,038.10