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 $243.35   7.691%   $262.066   $262.07   $262.05   $262.10  
  Purchase #2 $49.69   7.476%   $53.4048   $53.40   $53.40   $53.40  
  Purchase #3 $38.38   4.778%   $40.2138   $40.21   $40.20   $40.20  
  Purchase #4 $84.98   6.206%   $90.2539   $90.25   $90.25   $90.30  
  Purchase #5 $58.71   10.144%   $64.6655   $64.67   $64.65   $64.70  
  Purchase #6 $187.26   7.341%   $201.0068   $201.01   $201.00   $201.00  
  Purchase #7 $213.27   9.243%   $232.9825   $232.98   $233.00   $233.00  
  7 purchase totals = $875.64       $944.5933   $944.59   $944.55   $944.70