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 $69.49   11.810%   $77.6968   $77.70   $77.70   $77.70  
  Purchase #2 $226.39   10.492%   $250.1428   $250.14   $250.15   $250.10  
  Purchase #3 $231.46   5.174%   $243.4357   $243.44   $243.45   $243.40  
  Purchase #4 $172.40   5.154%   $181.2855   $181.29   $181.30   $181.30  
  Purchase #5 $97.54   12.789%   $110.0144   $110.01   $110.00   $110.00  
  Purchase #6 $119.70   5.613%   $126.4188   $126.42   $126.40   $126.40  
  Purchase #7 $45.60   3.173%   $47.0469   $47.05   $47.05   $47.00  
  7 purchase totals = $962.58       $1,036.0409   $1,036.05   $1,036.05   $1,035.90