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 $61.67   12.371%   $69.2992   $69.30   $69.30   $69.30  
  Purchase #2 $174.83   11.518%   $194.9669   $194.97   $194.95   $195.00  
  Purchase #3 $232.36   5.261%   $244.5845   $244.58   $244.60   $244.60  
  Purchase #4 $85.69   4.484%   $89.5323   $89.53   $89.55   $89.50  
  Purchase #5 $93.33   12.480%   $104.9776   $104.98   $105.00   $105.00  
  Purchase #6 $15.52   5.838%   $16.4261   $16.43   $16.45   $16.40  
  Purchase #7 $15.97   9.417%   $17.4739   $17.47   $17.45   $17.50  
  7 purchase totals = $679.37       $737.2605   $737.26   $737.30   $737.30