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 $181.42   13.116%   $205.215   $205.22   $205.20   $205.20  
  Purchase #2 $113.47   9.175%   $123.8809   $123.88   $123.90   $123.90  
  Purchase #3 $51.94   3.282%   $53.6447   $53.64   $53.65   $53.60  
  Purchase #4 $13.34   6.841%   $14.2526   $14.25   $14.25   $14.30  
  Purchase #5 $49.67   3.805%   $51.5599   $51.56   $51.55   $51.60  
  Purchase #6 $195.97   7.544%   $210.754   $210.75   $210.75   $210.80  
  Purchase #7 $96.48   5.531%   $101.8163   $101.82   $101.80   $101.80  
  7 purchase totals = $702.29       $761.1234   $761.12   $761.10   $761.20