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 $66.57   11.433%   $74.1809   $74.18   $74.20   $74.20  
  Purchase #2 $97.66   10.380%   $107.7971   $107.80   $107.80   $107.80  
  Purchase #3 $30.29   11.382%   $33.7376   $33.74   $33.75   $33.70  
  Purchase #4 $223.27   7.715%   $240.4953   $240.50   $240.50   $240.50  
  Purchase #5 $157.85   9.509%   $172.86   $172.86   $172.85   $172.90  
  Purchase #6 $9.29   13.431%   $10.5377   $10.54   $10.55   $10.50  
  Purchase #7 $146.35   7.152%   $156.817   $156.82   $156.80   $156.80  
  7 purchase totals = $731.28       $796.4256   $796.44   $796.45   $796.40