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 $62.78   9.325%   $68.6342   $68.63   $68.65   $68.60  
  Purchase #2 $146.91   10.377%   $162.1549   $162.15   $162.15   $162.20  
  Purchase #3 $193.77   4.788%   $203.0477   $203.05   $203.05   $203.00  
  Purchase #4 $204.67   3.252%   $211.3259   $211.33   $211.35   $211.30  
  Purchase #5 $47.85   3.694%   $49.6176   $49.62   $49.60   $49.60  
  Purchase #6 $77.78   13.274%   $88.1045   $88.10   $88.10   $88.10  
  Purchase #7 $95.47   7.299%   $102.4384   $102.44   $102.45   $102.40  
  7 purchase totals = $829.23       $885.3232   $885.32   $885.35   $885.20