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 $77.35   12.413%   $86.9515   $86.95   $86.95   $87.00  
  Purchase #2 $185.25   8.481%   $200.9611   $200.96   $200.95   $201.00  
  Purchase #3 $54.96   3.843%   $57.0721   $57.07   $57.05   $57.10  
  Purchase #4 $172.27   11.705%   $192.4342   $192.43   $192.45   $192.40  
  Purchase #5 $33.61   6.678%   $35.8545   $35.85   $35.85   $35.90  
  Purchase #6 $236.94   3.678%   $245.6547   $245.65   $245.65   $245.70  
  Purchase #7 $220.95   10.103%   $243.2726   $243.27   $243.25   $243.30  
  7 purchase totals = $981.33       $1,062.2007   $1,062.18   $1,062.15   $1,062.40