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 $182.40   6.528%   $194.3071   $194.31   $194.30   $194.30  
  Purchase #2 $213.57   3.654%   $221.3738   $221.37   $221.35   $221.40  
  Purchase #3 $239.59   11.718%   $267.6652   $267.67   $267.65   $267.70  
  Purchase #4 $171.94   4.412%   $179.526   $179.53   $179.55   $179.50  
  Purchase #5 $245.34   10.154%   $270.2518   $270.25   $270.25   $270.30  
  Purchase #6 $92.48   6.456%   $98.4505   $98.45   $98.45   $98.50  
  Purchase #7 $24.43   6.414%   $25.9969   $26.00   $26.00   $26.00  
  7 purchase totals = $1,169.75       $1,257.5713   $1,257.58   $1,257.55   $1,257.70