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 $57.32   8.591%   $62.2444   $62.24   $62.25   $62.20  
  Purchase #2 $196.29   5.283%   $206.66   $206.66   $206.65   $206.70  
  Purchase #3 $240.35   7.509%   $258.3979   $258.40   $258.40   $258.40  
  Purchase #4 $226.73   7.487%   $243.7053   $243.71   $243.70   $243.70  
  Purchase #5 $66.95   7.625%   $72.0549   $72.05   $72.05   $72.10  
  Purchase #6 $167.42   9.637%   $183.5543   $183.55   $183.55   $183.60  
  Purchase #7 $115.89   3.792%   $120.2845   $120.28   $120.30   $120.30  
  7 purchase totals = $1,070.95       $1,146.9013   $1,146.89   $1,146.90   $1,147.00