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 $101.38   10.460%   $111.9843   $111.98   $112.00   $112.00  
  Purchase #2 $124.93   13.621%   $141.9467   $141.95   $141.95   $141.90  
  Purchase #3 $49.26   10.461%   $54.4131   $54.41   $54.40   $54.40  
  Purchase #4 $165.48   5.873%   $175.1986   $175.20   $175.20   $175.20  
  Purchase #5 $182.27   12.649%   $205.3253   $205.33   $205.35   $205.30  
  Purchase #6 $95.81   8.297%   $103.7594   $103.76   $103.75   $103.80  
  Purchase #7 $13.49   4.395%   $14.0829   $14.08   $14.10   $14.10  
  7 purchase totals = $732.62       $806.7103   $806.71   $806.75   $806.70