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 $53.95   11.570%   $60.192   $60.19   $60.20   $60.20  
  Purchase #2 $84.74   9.341%   $92.6556   $92.66   $92.65   $92.70  
  Purchase #3 $195.80   5.793%   $207.1427   $207.14   $207.15   $207.10  
  Purchase #4 $218.68   7.803%   $235.7436   $235.74   $235.75   $235.70  
  Purchase #5 $7.25   3.329%   $7.4914   $7.49   $7.50   $7.50  
  Purchase #6 $131.47   6.509%   $140.0274   $140.03   $140.05   $140.00  
  Purchase #7 $241.80   11.805%   $270.3445   $270.34   $270.35   $270.30  
  7 purchase totals = $933.69       $1,013.5972   $1,013.59   $1,013.65   $1,013.50