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 $88.46   7.441%   $95.0423   $95.04   $95.05   $95.00  
  Purchase #2 $61.73   8.126%   $66.7462   $66.75   $66.75   $66.70  
  Purchase #3 $49.91   13.494%   $56.6449   $56.64   $56.65   $56.60  
  Purchase #4 $156.64   4.155%   $163.1484   $163.15   $163.15   $163.10  
  Purchase #5 $17.77   6.818%   $18.9816   $18.98   $19.00   $19.00  
  Purchase #6 $124.64   9.172%   $136.072   $136.07   $136.05   $136.10  
  Purchase #7 $209.68   3.422%   $216.8552   $216.86   $216.85   $216.90  
  7 purchase totals = $708.83       $753.4906   $753.49   $753.50   $753.40