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 $68.38   7.145%   $73.2658   $73.27   $73.25   $73.30  
  Purchase #2 $54.26   7.497%   $58.3279   $58.33   $58.35   $58.30  
  Purchase #3 $205.54   10.287%   $226.6839   $226.68   $226.70   $226.70  
  Purchase #4 $223.52   7.177%   $239.562   $239.56   $239.55   $239.60  
  Purchase #5 $141.35   11.556%   $157.6844   $157.68   $157.70   $157.70  
  Purchase #6 $179.66   8.353%   $194.667   $194.67   $194.65   $194.70  
  Purchase #7 $191.74   3.479%   $198.4106   $198.41   $198.40   $198.40  
  7 purchase totals = $1,064.45       $1,148.6016   $1,148.60   $1,148.60   $1,148.70