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 $88.73   8.243%   $96.044   $96.04   $96.05   $96.00  
  Purchase #2 $213.60   13.735%   $242.938   $242.94   $242.95   $242.90  
  Purchase #3 $182.65   9.852%   $200.6447   $200.64   $200.65   $200.60  
  Purchase #4 $165.51   3.251%   $170.8907   $170.89   $170.90   $170.90  
  Purchase #5 $20.96   8.536%   $22.7491   $22.75   $22.75   $22.70  
  Purchase #6 $144.69   8.545%   $157.0538   $157.05   $157.05   $157.10  
  Purchase #7 $155.99   12.154%   $174.949   $174.95   $174.95   $174.90  
  7 purchase totals = $972.13       $1,065.2693   $1,065.26   $1,065.30   $1,065.10