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 $236.44   7.404%   $253.946   $253.95   $253.95   $253.90  
  Purchase #2 $59.42   6.512%   $63.2894   $63.29   $63.30   $63.30  
  Purchase #3 $130.49   4.135%   $135.8858   $135.89   $135.90   $135.90  
  Purchase #4 $202.62   11.141%   $225.1939   $225.19   $225.20   $225.20  
  Purchase #5 $227.74   11.558%   $254.0622   $254.06   $254.05   $254.10  
  Purchase #6 $43.29   7.119%   $46.3718   $46.37   $46.35   $46.40  
  Purchase #7 $31.62   12.854%   $35.6844   $35.68   $35.70   $35.70  
  7 purchase totals = $931.62       $1,014.4335   $1,014.43   $1,014.45   $1,014.50