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 $182.77   7.251%   $196.0227   $196.02   $196.00   $196.00  
  Purchase #2 $22.57   3.146%   $23.2801   $23.28   $23.30   $23.30  
  Purchase #3 $193.43   6.239%   $205.4981   $205.50   $205.50   $205.50  
  Purchase #4 $79.30   4.408%   $82.7955   $82.80   $82.80   $82.80  
  Purchase #5 $118.88   13.470%   $134.8931   $134.89   $134.90   $134.90  
  Purchase #6 $130.37   10.621%   $144.2166   $144.22   $144.20   $144.20  
  Purchase #7 $160.52   9.596%   $175.9235   $175.92   $175.90   $175.90  
  7 purchase totals = $887.84       $962.6296   $962.63   $962.60   $962.60