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 $197.78   8.556%   $214.7021   $214.70   $214.70   $214.70  
  Purchase #2 $86.35   10.657%   $95.5523   $95.55   $95.55   $95.60  
  Purchase #3 $51.91   7.154%   $55.6236   $55.62   $55.60   $55.60  
  Purchase #4 $178.52   12.576%   $200.9707   $200.97   $200.95   $201.00  
  Purchase #5 $232.34   11.729%   $259.5912   $259.59   $259.60   $259.60  
  Purchase #6 $224.85   12.868%   $253.7837   $253.78   $253.80   $253.80  
  Purchase #7 $158.64   11.349%   $176.6441   $176.64   $176.65   $176.60  
  7 purchase totals = $1,130.39       $1,256.8677   $1,256.85   $1,256.85   $1,256.90