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 $213.86   11.175%   $237.7589   $237.76   $237.75   $237.80  
  Purchase #2 $66.86   9.659%   $73.318   $73.32   $73.30   $73.30  
  Purchase #3 $95.29   9.107%   $103.9681   $103.97   $103.95   $104.00  
  Purchase #4 $177.64   13.807%   $202.1668   $202.17   $202.15   $202.20  
  Purchase #5 $23.26   5.753%   $24.5981   $24.60   $24.60   $24.60  
  Purchase #6 $84.27   7.521%   $90.6079   $90.61   $90.60   $90.60  
  Purchase #7 $195.94   3.521%   $202.839   $202.84   $202.85   $202.80  
  7 purchase totals = $857.12       $935.2568   $935.27   $935.20   $935.30