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 $84.47   13.127%   $95.5584   $95.56   $95.55   $95.60  
  Purchase #2 $11.41   5.774%   $12.0688   $12.07   $12.05   $12.10  
  Purchase #3 $111.70   8.863%   $121.6   $121.60   $121.60   $121.60  
  Purchase #4 $204.41   3.401%   $211.362   $211.36   $211.35   $211.40  
  Purchase #5 $249.27   12.630%   $280.7528   $280.75   $280.75   $280.80  
  Purchase #6 $148.77   5.542%   $157.0148   $157.01   $157.00   $157.00  
  Purchase #7 $134.80   7.479%   $144.8817   $144.88   $144.90   $144.90  
  7 purchase totals = $944.83       $1,023.2385   $1,023.23   $1,023.20   $1,023.40