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 $68.89   12.173%   $77.276   $77.28   $77.30   $77.30  
  Purchase #2 $202.53   7.601%   $217.9243   $217.92   $217.90   $217.90  
  Purchase #3 $79.59   10.297%   $87.7854   $87.79   $87.80   $87.80  
  Purchase #4 $250.82   6.500%   $267.1233   $267.12   $267.10   $267.10  
  Purchase #5 $214.46   8.440%   $232.5604   $232.56   $232.55   $232.60  
  Purchase #6 $40.85   9.724%   $44.8223   $44.82   $44.80   $44.80  
  Purchase #7 $208.47   8.631%   $226.463   $226.46   $226.45   $226.50  
  7 purchase totals = $1,065.61       $1,153.9547   $1,153.95   $1,153.90   $1,154.00