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 $95.58   6.469%   $101.7631   $101.76   $101.75   $101.80  
  Purchase #2 $240.46   9.604%   $263.5538   $263.55   $263.55   $263.60  
  Purchase #3 $245.34   3.184%   $253.1516   $253.15   $253.15   $253.20  
  Purchase #4 $102.94   8.550%   $111.7414   $111.74   $111.75   $111.70  
  Purchase #5 $95.27   6.499%   $101.4616   $101.46   $101.45   $101.50  
  Purchase #6 $25.67   9.360%   $28.0727   $28.07   $28.05   $28.10  
  Purchase #7 $232.67   5.119%   $244.5804   $244.58   $244.60   $244.60  
  7 purchase totals = $1,037.93       $1,104.3246   $1,104.31   $1,104.30   $1,104.50