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 $43.52   6.440%   $46.3227   $46.32   $46.30   $46.30  
  Purchase #2 $165.77   8.793%   $180.3462   $180.35   $180.35   $180.30  
  Purchase #3 $182.74   5.823%   $193.381   $193.38   $193.40   $193.40  
  Purchase #4 $115.65   3.597%   $119.8099   $119.81   $119.80   $119.80  
  Purchase #5 $54.27   11.667%   $60.6017   $60.60   $60.60   $60.60  
  Purchase #6 $114.82   13.489%   $130.3081   $130.31   $130.30   $130.30  
  Purchase #7 $23.26   3.573%   $24.0911   $24.09   $24.10   $24.10  
  7 purchase totals = $700.03       $754.8607   $754.86   $754.85   $754.80