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 $76.36   13.781%   $86.8832   $86.88   $86.90   $86.90  
  Purchase #2 $205.95   3.117%   $212.3695   $212.37   $212.35   $212.40  
  Purchase #3 $41.97   10.540%   $46.3936   $46.39   $46.40   $46.40  
  Purchase #4 $91.87   6.198%   $97.5641   $97.56   $97.55   $97.60  
  Purchase #5 $181.91   10.615%   $201.2197   $201.22   $201.20   $201.20  
  Purchase #6 $176.27   13.762%   $200.5283   $200.53   $200.55   $200.50  
  Purchase #7 $156.51   13.161%   $177.1083   $177.11   $177.10   $177.10  
  7 purchase totals = $930.84       $1,022.0667   $1,022.06   $1,022.05   $1,022.10