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 $60.37   3.746%   $62.6315   $62.63   $62.65   $62.60  
  Purchase #2 $229.48   10.833%   $254.3396   $254.34   $254.35   $254.30  
  Purchase #3 $101.54   9.567%   $111.2543   $111.25   $111.25   $111.30  
  Purchase #4 $205.77   12.567%   $231.6291   $231.63   $231.65   $231.60  
  Purchase #5 $141.33   8.750%   $153.6964   $153.70   $153.70   $153.70  
  Purchase #6 $214.50   7.659%   $230.9286   $230.93   $230.95   $230.90  
  Purchase #7 $100.43   8.528%   $108.9947   $108.99   $109.00   $109.00  
  7 purchase totals = $1,053.42       $1,153.4742   $1,153.47   $1,153.55   $1,153.40