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 $67.53   10.365%   $74.5295   $74.53   $74.55   $74.50  
  Purchase #2 $23.34   11.773%   $26.0878   $26.09   $26.10   $26.10  
  Purchase #3 $24.98   8.622%   $27.1338   $27.13   $27.15   $27.10  
  Purchase #4 $142.29   3.529%   $147.3114   $147.31   $147.30   $147.30  
  Purchase #5 $178.81   8.865%   $194.6615   $194.66   $194.65   $194.70  
  Purchase #6 $166.86   6.226%   $177.2487   $177.25   $177.25   $177.20  
  Purchase #7 $56.30   3.593%   $58.3229   $58.32   $58.30   $58.30  
  7 purchase totals = $660.11       $705.2956   $705.29   $705.30   $705.20