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 $73.25   4.260%   $76.3705   $76.37   $76.35   $76.40  
  Purchase #2 $211.83   12.622%   $238.5672   $238.57   $238.55   $238.60  
  Purchase #3 $180.43   9.474%   $197.5239   $197.52   $197.50   $197.50  
  Purchase #4 $196.26   4.328%   $204.7541   $204.75   $204.75   $204.80  
  Purchase #5 $112.59   3.178%   $116.1681   $116.17   $116.15   $116.20  
  Purchase #6 $76.82   12.146%   $86.1506   $86.15   $86.15   $86.20  
  Purchase #7 $113.73   11.615%   $126.9397   $126.94   $126.95   $126.90  
  7 purchase totals = $964.91       $1,046.4741   $1,046.47   $1,046.40   $1,046.60