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 $60.96   4.362%   $63.6191   $63.62   $63.60   $63.60  
  Purchase #2 $113.96   9.423%   $124.6985   $124.70   $124.70   $124.70  
  Purchase #3 $36.67   7.160%   $39.2956   $39.30   $39.30   $39.30  
  Purchase #4 $33.92   4.401%   $35.4128   $35.41   $35.40   $35.40  
  Purchase #5 $77.42   5.494%   $81.6735   $81.67   $81.65   $81.70  
  Purchase #6 $66.47   5.796%   $70.3226   $70.32   $70.30   $70.30  
  Purchase #7 $56.90   8.835%   $61.9271   $61.93   $61.95   $61.90  
  7 purchase totals = $446.30       $476.9492   $476.95   $476.90   $476.90