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 $62.82   10.630%   $69.4978   $69.50   $69.50   $69.50  
  Purchase #2 $238.36   13.102%   $269.5899   $269.59   $269.60   $269.60  
  Purchase #3 $144.82   11.175%   $161.0036   $161.00   $161.00   $161.00  
  Purchase #4 $58.33   12.451%   $65.5927   $65.59   $65.60   $65.60  
  Purchase #5 $135.89   5.181%   $142.9305   $142.93   $142.95   $142.90  
  Purchase #6 $93.48   7.633%   $100.6153   $100.62   $100.60   $100.60  
  Purchase #7 $240.48   5.179%   $252.9345   $252.93   $252.95   $252.90  
  7 purchase totals = $974.18       $1,062.1643   $1,062.16   $1,062.20   $1,062.10