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 $112.60   11.584%   $125.6436   $125.64   $125.65   $125.60  
  Purchase #2 $213.50   11.404%   $237.8475   $237.85   $237.85   $237.80  
  Purchase #3 $114.44   7.687%   $123.237   $123.24   $123.25   $123.20  
  Purchase #4 $46.33   9.773%   $50.8578   $50.86   $50.85   $50.90  
  Purchase #5 $49.29   9.160%   $53.805   $53.81   $53.80   $53.80  
  Purchase #6 $147.98   13.115%   $167.3876   $167.39   $167.40   $167.40  
  Purchase #7 $174.47   9.804%   $191.575   $191.58   $191.60   $191.60  
  7 purchase totals = $858.61       $950.3535   $950.37   $950.40   $950.30