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 $217.36   12.684%   $244.9299   $244.93   $244.95   $244.90  
  Purchase #2 $36.66   6.652%   $39.0986   $39.10   $39.10   $39.10  
  Purchase #3 $49.80   13.829%   $56.6868   $56.69   $56.70   $56.70  
  Purchase #4 $29.66   3.181%   $30.6035   $30.60   $30.60   $30.60  
  Purchase #5 $219.53   7.597%   $236.2077   $236.21   $236.20   $236.20  
  Purchase #6 $194.37   7.515%   $208.9769   $208.98   $209.00   $209.00  
  Purchase #7 $197.62   4.842%   $207.1888   $207.19   $207.20   $207.20  
  7 purchase totals = $945.00       $1,023.6922   $1,023.70   $1,023.75   $1,023.70