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 $152.67   10.696%   $168.9996   $169.00   $169.00   $169.00  
  Purchase #2 $181.26   5.796%   $191.7658   $191.77   $191.75   $191.80  
  Purchase #3 $59.70   7.454%   $64.15   $64.15   $64.15   $64.20  
  Purchase #4 $187.78   5.299%   $197.7305   $197.73   $197.75   $197.70  
  Purchase #5 $13.53   5.501%   $14.2743   $14.27   $14.25   $14.30  
  Purchase #6 $200.69   9.481%   $219.7174   $219.72   $219.70   $219.70  
  Purchase #7 $220.32   13.714%   $250.5347   $250.53   $250.55   $250.50  
  7 purchase totals = $1,015.95       $1,107.1723   $1,107.17   $1,107.15   $1,107.20