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 $195.81   9.468%   $214.3493   $214.35   $214.35   $214.30  
  Purchase #2 $52.30   12.140%   $58.6492   $58.65   $58.65   $58.60  
  Purchase #3 $184.27   6.744%   $196.6972   $196.70   $196.70   $196.70  
  Purchase #4 $244.98   3.253%   $252.9492   $252.95   $252.95   $252.90  
  Purchase #5 $246.90   9.773%   $271.0295   $271.03   $271.05   $271.00  
  Purchase #6 $165.31   9.206%   $180.5284   $180.53   $180.55   $180.50  
  Purchase #7 $69.33   8.176%   $74.9984   $75.00   $75.00   $75.00  
  7 purchase totals = $1,158.90       $1,249.2012   $1,249.21   $1,249.25   $1,249.00