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 $116.71   7.322%   $125.2555   $125.26   $125.25   $125.30  
  Purchase #2 $59.79   5.460%   $63.0545   $63.05   $63.05   $63.10  
  Purchase #3 $200.62   3.467%   $207.5755   $207.58   $207.60   $207.60  
  Purchase #4 $118.45   7.548%   $127.3906   $127.39   $127.40   $127.40  
  Purchase #5 $155.93   4.506%   $162.9562   $162.96   $162.95   $163.00  
  Purchase #6 $120.36   8.122%   $130.1356   $130.14   $130.15   $130.10  
  Purchase #7 $176.45   8.743%   $191.877   $191.88   $191.90   $191.90  
  7 purchase totals = $948.31       $1,008.2449   $1,008.26   $1,008.30   $1,008.40