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 $63.33   8.443%   $68.677   $68.68   $68.70   $68.70  
  Purchase #2 $180.30   9.457%   $197.351   $197.35   $197.35   $197.40  
  Purchase #3 $220.91   11.813%   $247.0061   $247.01   $247.00   $247.00  
  Purchase #4 $62.29   5.596%   $65.7757   $65.78   $65.80   $65.80  
  Purchase #5 $221.40   5.782%   $234.2013   $234.20   $234.20   $234.20  
  Purchase #6 $164.48   11.436%   $183.2899   $183.29   $183.30   $183.30  
  Purchase #7 $222.61   6.294%   $236.6211   $236.62   $236.60   $236.60  
  7 purchase totals = $1,135.32       $1,232.9221   $1,232.93   $1,232.95   $1,233.00