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 $74.37   10.613%   $82.2629   $82.26   $82.25   $82.30  
  Purchase #2 $176.49   10.827%   $195.5986   $195.60   $195.60   $195.60  
  Purchase #3 $91.93   3.254%   $94.9214   $94.92   $94.90   $94.90  
  Purchase #4 $94.74   13.295%   $107.3357   $107.34   $107.35   $107.30  
  Purchase #5 $130.27   8.300%   $141.0824   $141.08   $141.10   $141.10  
  Purchase #6 $56.46   9.661%   $61.9146   $61.91   $61.90   $61.90  
  Purchase #7 $48.61   11.392%   $54.1477   $54.15   $54.15   $54.10  
  7 purchase totals = $672.87       $737.2633   $737.26   $737.25   $737.20