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 $92.67   3.570%   $95.9783   $95.98   $96.00   $96.00  
  Purchase #2 $217.56   10.772%   $240.9956   $241.00   $241.00   $241.00  
  Purchase #3 $99.53   5.633%   $105.1365   $105.14   $105.15   $105.10  
  Purchase #4 $241.64   9.572%   $264.7698   $264.77   $264.75   $264.80  
  Purchase #5 $138.70   12.520%   $156.0652   $156.07   $156.05   $156.10  
  Purchase #6 $90.92   11.163%   $101.0694   $101.07   $101.05   $101.10  
  Purchase #7 $103.80   3.540%   $107.4745   $107.47   $107.45   $107.50  
  7 purchase totals = $984.82       $1,071.4893   $1,071.50   $1,071.45   $1,071.60