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 $85.86   9.381%   $93.9145   $93.91   $93.90   $93.90  
  Purchase #2 $211.29   7.839%   $227.853   $227.85   $227.85   $227.90  
  Purchase #3 $71.94   7.546%   $77.3686   $77.37   $77.35   $77.40  
  Purchase #4 $92.47   10.271%   $101.9676   $101.97   $101.95   $102.00  
  Purchase #5 $12.44   9.333%   $13.601   $13.60   $13.60   $13.60  
  Purchase #6 $235.98   3.377%   $243.949   $243.95   $243.95   $243.90  
  Purchase #7 $239.57   5.555%   $252.8781   $252.88   $252.90   $252.90  
  7 purchase totals = $949.55       $1,011.5318   $1,011.53   $1,011.50   $1,011.60