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 $61.26   10.622%   $67.767   $67.77   $67.75   $67.80  
  Purchase #2 $223.80   4.679%   $234.2716   $234.27   $234.25   $234.30  
  Purchase #3 $121.81   8.781%   $132.5061   $132.51   $132.50   $132.50  
  Purchase #4 $76.86   9.320%   $84.0234   $84.02   $84.00   $84.00  
  Purchase #5 $167.42   10.813%   $185.5231   $185.52   $185.50   $185.50  
  Purchase #6 $33.68   8.480%   $36.5361   $36.54   $36.55   $36.50  
  Purchase #7 $58.64   9.751%   $64.358   $64.36   $64.35   $64.40  
  7 purchase totals = $743.47       $804.9853   $804.99   $804.90   $805.00