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 $194.97   5.562%   $205.8142   $205.81   $205.80   $205.80  
  Purchase #2 $217.69   5.334%   $229.3016   $229.30   $229.30   $229.30  
  Purchase #3 $232.76   6.695%   $248.3433   $248.34   $248.35   $248.30  
  Purchase #4 $118.59   4.147%   $123.5079   $123.51   $123.50   $123.50  
  Purchase #5 $244.78   11.387%   $272.6531   $272.65   $272.65   $272.70  
  Purchase #6 $19.34   9.571%   $21.191   $21.19   $21.20   $21.20  
  Purchase #7 $247.28   10.720%   $273.7884   $273.79   $273.80   $273.80  
  7 purchase totals = $1,275.41       $1,374.5995   $1,374.59   $1,374.60   $1,374.60