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 $108.49   8.716%   $117.946   $117.95   $117.95   $117.90  
  Purchase #2 $132.71   11.271%   $147.6677   $147.67   $147.65   $147.70  
  Purchase #3 $39.52   13.466%   $44.8418   $44.84   $44.85   $44.80  
  Purchase #4 $71.86   5.160%   $75.568   $75.57   $75.55   $75.60  
  Purchase #5 $115.67   9.834%   $127.045   $127.05   $127.05   $127.00  
  Purchase #6 $131.29   5.476%   $138.4794   $138.48   $138.50   $138.50  
  Purchase #7 $118.73   3.576%   $122.9758   $122.98   $123.00   $123.00  
  7 purchase totals = $718.27       $774.5237   $774.54   $774.55   $774.50