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 $119.71   5.443%   $126.2258   $126.23   $126.25   $126.20  
  Purchase #2 $103.48   13.355%   $117.2998   $117.30   $117.30   $117.30  
  Purchase #3 $44.92   12.543%   $50.5543   $50.55   $50.55   $50.60  
  Purchase #4 $65.36   7.493%   $70.2574   $70.26   $70.25   $70.30  
  Purchase #5 $192.62   4.531%   $201.3476   $201.35   $201.35   $201.30  
  Purchase #6 $205.99   6.429%   $219.2331   $219.23   $219.25   $219.20  
  Purchase #7 $55.90   12.364%   $62.8115   $62.81   $62.80   $62.80  
  7 purchase totals = $787.98       $847.7295   $847.73   $847.75   $847.70