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 $205.27   13.866%   $233.7327   $233.73   $233.75   $233.70  
  Purchase #2 $126.51   4.542%   $132.2561   $132.26   $132.25   $132.30  
  Purchase #3 $95.88   11.581%   $106.9839   $106.98   $107.00   $107.00  
  Purchase #4 $217.26   8.108%   $234.8754   $234.88   $234.90   $234.90  
  Purchase #5 $119.66   13.207%   $135.4635   $135.46   $135.45   $135.50  
  Purchase #6 $13.53   6.764%   $14.4452   $14.45   $14.45   $14.40  
  Purchase #7 $86.74   6.829%   $92.6635   $92.66   $92.65   $92.70  
  7 purchase totals = $864.85       $950.4203   $950.42   $950.45   $950.50