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 $14.64   11.632%   $16.3429   $16.34   $16.35   $16.30  
  Purchase #2 $62.45   11.737%   $69.7798   $69.78   $69.80   $69.80  
  Purchase #3 $28.98   4.604%   $30.3142   $30.31   $30.30   $30.30  
  Purchase #4 $166.76   9.196%   $182.0952   $182.10   $182.10   $182.10  
  Purchase #5 $158.90   11.596%   $177.326   $177.33   $177.35   $177.30  
  Purchase #6 $246.31   8.410%   $267.0247   $267.02   $267.00   $267.00  
  Purchase #7 $24.60   7.533%   $26.4531   $26.45   $26.45   $26.50  
  7 purchase totals = $702.64       $769.3359   $769.33   $769.35   $769.30