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 $96.96   5.848%   $102.6302   $102.63   $102.65   $102.60  
  Purchase #2 $205.81   5.291%   $216.6994   $216.70   $216.70   $216.70  
  Purchase #3 $160.89   9.589%   $176.3177   $176.32   $176.30   $176.30  
  Purchase #4 $165.45   7.705%   $178.1979   $178.20   $178.20   $178.20  
  Purchase #5 $173.90   4.552%   $181.8159   $181.82   $181.80   $181.80  
  Purchase #6 $171.97   11.119%   $191.0913   $191.09   $191.10   $191.10  
  Purchase #7 $249.34   11.626%   $278.3283   $278.33   $278.35   $278.30  
  7 purchase totals = $1,224.32       $1,325.0807   $1,325.09   $1,325.10   $1,325.00