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 $114.52   4.464%   $119.6322   $119.63   $119.65   $119.60  
  Purchase #2 $168.68   10.440%   $186.2902   $186.29   $186.30   $186.30  
  Purchase #3 $193.33   12.505%   $217.5059   $217.51   $217.50   $217.50  
  Purchase #4 $204.44   4.183%   $212.9917   $212.99   $213.00   $213.00  
  Purchase #5 $224.80   12.233%   $252.2998   $252.30   $252.30   $252.30  
  Purchase #6 $201.46   9.115%   $219.8231   $219.82   $219.80   $219.80  
  Purchase #7 $135.51   7.179%   $145.2383   $145.24   $145.25   $145.20  
  7 purchase totals = $1,242.74       $1,353.7812   $1,353.78   $1,353.80   $1,353.70