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 $217.56   7.856%   $234.6515   $234.65   $234.65   $234.70  
  Purchase #2 $150.92   4.255%   $157.3416   $157.34   $157.35   $157.30  
  Purchase #3 $104.38   13.336%   $118.3001   $118.30   $118.30   $118.30  
  Purchase #4 $87.31   3.573%   $90.4296   $90.43   $90.45   $90.40  
  Purchase #5 $102.98   7.354%   $110.5531   $110.55   $110.55   $110.60  
  Purchase #6 $75.86   13.871%   $86.3825   $86.38   $86.40   $86.40  
  Purchase #7 $228.77   3.272%   $236.2554   $236.26   $236.25   $236.30  
  7 purchase totals = $967.78       $1,033.9138   $1,033.91   $1,033.95   $1,034.00