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 $41.56   6.515%   $44.2676   $44.27   $44.25   $44.30  
  Purchase #2 $221.52   12.280%   $248.7227   $248.72   $248.70   $248.70  
  Purchase #3 $95.60   9.748%   $104.9191   $104.92   $104.90   $104.90  
  Purchase #4 $88.86   9.637%   $97.4234   $97.42   $97.40   $97.40  
  Purchase #5 $160.73   11.583%   $179.3474   $179.35   $179.35   $179.30  
  Purchase #6 $118.60   5.605%   $125.2475   $125.25   $125.25   $125.20  
  Purchase #7 $192.68   4.148%   $200.6724   $200.67   $200.65   $200.70  
  7 purchase totals = $919.55       $1,000.6001   $1,000.60   $1,000.50   $1,000.50