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 $198.45   5.434%   $209.2338   $209.23   $209.25   $209.20  
  Purchase #2 $101.97   11.452%   $113.6476   $113.65   $113.65   $113.60  
  Purchase #3 $62.84   7.337%   $67.4506   $67.45   $67.45   $67.50  
  Purchase #4 $60.70   7.233%   $65.0904   $65.09   $65.10   $65.10  
  Purchase #5 $41.31   12.281%   $46.3833   $46.38   $46.40   $46.40  
  Purchase #6 $14.29   10.268%   $15.7573   $15.76   $15.75   $15.80  
  Purchase #7 $219.66   4.839%   $230.2893   $230.29   $230.30   $230.30  
  7 purchase totals = $699.22       $747.8523   $747.85   $747.90   $747.90