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 $84.60   13.590%   $96.0971   $96.10   $96.10   $96.10  
  Purchase #2 $93.68   13.215%   $106.0598   $106.06   $106.05   $106.10  
  Purchase #3 $160.58   13.439%   $182.1603   $182.16   $182.15   $182.20  
  Purchase #4 $166.82   9.548%   $182.748   $182.75   $182.75   $182.70  
  Purchase #5 $214.62   6.421%   $228.4008   $228.40   $228.40   $228.40  
  Purchase #6 $64.43   5.455%   $67.9447   $67.94   $67.95   $67.90  
  Purchase #7 $193.32   6.243%   $205.389   $205.39   $205.40   $205.40  
  7 purchase totals = $978.05       $1,068.7997   $1,068.80   $1,068.80   $1,068.80