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 $82.91   11.666%   $92.5823   $92.58   $92.60   $92.60  
  Purchase #2 $86.97   7.532%   $93.5206   $93.52   $93.50   $93.50  
  Purchase #3 $197.98   12.844%   $223.4086   $223.41   $223.40   $223.40  
  Purchase #4 $33.64   9.593%   $36.8671   $36.87   $36.85   $36.90  
  Purchase #5 $209.25   6.560%   $222.9768   $222.98   $223.00   $223.00  
  Purchase #6 $245.32   6.866%   $262.1637   $262.16   $262.15   $262.20  
  Purchase #7 $74.55   11.452%   $83.0875   $83.09   $83.10   $83.10  
  7 purchase totals = $930.62       $1,014.6066   $1,014.61   $1,014.60   $1,014.70