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 $206.76   11.625%   $230.7959   $230.80   $230.80   $230.80  
  Purchase #2 $131.26   11.761%   $146.6975   $146.70   $146.70   $146.70  
  Purchase #3 $62.36   3.811%   $64.7365   $64.74   $64.75   $64.70  
  Purchase #4 $10.46   7.847%   $11.2808   $11.28   $11.30   $11.30  
  Purchase #5 $213.85   10.852%   $237.057   $237.06   $237.05   $237.10  
  Purchase #6 $143.28   5.496%   $151.1547   $151.15   $151.15   $151.20  
  Purchase #7 $114.90   4.685%   $120.2831   $120.28   $120.30   $120.30  
  7 purchase totals = $882.87       $962.0055   $962.01   $962.05   $962.10