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 $68.95   11.282%   $76.7289   $76.73   $76.75   $76.70  
  Purchase #2 $234.69   3.617%   $243.1787   $243.18   $243.20   $243.20  
  Purchase #3 $208.82   3.483%   $216.0932   $216.09   $216.10   $216.10  
  Purchase #4 $211.51   10.312%   $233.3209   $233.32   $233.30   $233.30  
  Purchase #5 $106.31   11.231%   $118.2497   $118.25   $118.25   $118.20  
  Purchase #6 $113.46   8.432%   $123.0269   $123.03   $123.05   $123.00  
  Purchase #7 $49.96   9.114%   $54.5134   $54.51   $54.50   $54.50  
  7 purchase totals = $993.70       $1,065.1117   $1,065.11   $1,065.15   $1,065.00