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 $243.74   7.564%   $262.1765   $262.18   $262.20   $262.20  
  Purchase #2 $145.95   5.482%   $153.951   $153.95   $153.95   $154.00  
  Purchase #3 $91.72   13.102%   $103.7372   $103.74   $103.75   $103.70  
  Purchase #4 $53.59   9.172%   $58.5053   $58.51   $58.50   $58.50  
  Purchase #5 $68.72   5.454%   $72.468   $72.47   $72.45   $72.50  
  Purchase #6 $182.79   7.247%   $196.0368   $196.04   $196.05   $196.00  
  Purchase #7 $66.28   11.353%   $73.8048   $73.80   $73.80   $73.80  
  7 purchase totals = $852.79       $920.6796   $920.69   $920.70   $920.70