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 $62.91   11.567%   $70.1868   $70.19   $70.20   $70.20  
  Purchase #2 $76.46   12.455%   $85.9831   $85.98   $86.00   $86.00  
  Purchase #3 $80.90   12.128%   $90.7116   $90.71   $90.70   $90.70  
  Purchase #4 $194.38   6.803%   $207.6037   $207.60   $207.60   $207.60  
  Purchase #5 $160.26   7.183%   $171.7715   $171.77   $171.75   $171.80  
  Purchase #6 $203.42   5.774%   $215.1655   $215.17   $215.15   $215.20  
  Purchase #7 $219.51   3.373%   $226.9141   $226.91   $226.90   $226.90  
  7 purchase totals = $997.84       $1,068.3363   $1,068.33   $1,068.30   $1,068.40