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 $43.32   10.868%   $48.028   $48.03   $48.05   $48.00  
  Purchase #2 $118.44   12.857%   $133.6678   $133.67   $133.65   $133.70  
  Purchase #3 $77.82   4.284%   $81.1538   $81.15   $81.15   $81.20  
  Purchase #4 $71.30   13.521%   $80.9405   $80.94   $80.95   $80.90  
  Purchase #5 $120.93   12.381%   $135.9023   $135.90   $135.90   $135.90  
  Purchase #6 $231.64   4.141%   $241.2322   $241.23   $241.25   $241.20  
  Purchase #7 $209.79   9.507%   $229.7347   $229.73   $229.75   $229.70  
  7 purchase totals = $873.24       $950.6593   $950.65   $950.70   $950.60