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 $57.61   10.619%   $63.7276   $63.73   $63.75   $63.70  
  Purchase #2 $196.98   13.290%   $223.1586   $223.16   $223.15   $223.20  
  Purchase #3 $219.29   12.647%   $247.0236   $247.02   $247.00   $247.00  
  Purchase #4 $213.43   10.260%   $235.3279   $235.33   $235.35   $235.30  
  Purchase #5 $154.40   10.237%   $170.2059   $170.21   $170.20   $170.20  
  Purchase #6 $177.70   7.326%   $190.7183   $190.72   $190.70   $190.70  
  Purchase #7 $119.98   4.585%   $125.4811   $125.48   $125.50   $125.50  
  7 purchase totals = $1,139.39       $1,255.6430   $1,255.65   $1,255.65   $1,255.60