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 $82.52   4.184%   $85.9726   $85.97   $85.95   $86.00  
  Purchase #2 $170.40   9.138%   $185.9712   $185.97   $185.95   $186.00  
  Purchase #3 $94.60   11.375%   $105.3608   $105.36   $105.35   $105.40  
  Purchase #4 $205.92   6.636%   $219.5849   $219.58   $219.60   $219.60  
  Purchase #5 $67.63   3.161%   $69.7678   $69.77   $69.75   $69.80  
  Purchase #6 $73.85   11.376%   $82.2512   $82.25   $82.25   $82.30  
  Purchase #7 $246.71   11.873%   $276.0019   $276.00   $276.00   $276.00  
  7 purchase totals = $941.63       $1,024.9104   $1,024.90   $1,024.85   $1,025.10