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 $86.73   10.657%   $95.9728   $95.97   $95.95   $96.00  
  Purchase #2 $123.89   6.684%   $132.1708   $132.17   $132.15   $132.20  
  Purchase #3 $122.51   4.130%   $127.5697   $127.57   $127.55   $127.60  
  Purchase #4 $5.90   4.469%   $6.1637   $6.16   $6.15   $6.20  
  Purchase #5 $230.69   10.185%   $254.1858   $254.19   $254.20   $254.20  
  Purchase #6 $17.86   10.773%   $19.7841   $19.78   $19.80   $19.80  
  Purchase #7 $203.71   11.349%   $226.829   $226.83   $226.85   $226.80  
  7 purchase totals = $791.29       $862.6759   $862.67   $862.65   $862.80