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 $31.81   10.819%   $35.2515   $35.25   $35.25   $35.30  
  Purchase #2 $213.89   6.104%   $226.9458   $226.95   $226.95   $226.90  
  Purchase #3 $9.84   8.176%   $10.6445   $10.64   $10.65   $10.60  
  Purchase #4 $194.49   5.126%   $204.4596   $204.46   $204.45   $204.50  
  Purchase #5 $239.39   4.364%   $249.837   $249.84   $249.85   $249.80  
  Purchase #6 $161.59   13.837%   $183.9492   $183.95   $183.95   $183.90  
  Purchase #7 $131.31   13.528%   $149.0736   $149.07   $149.05   $149.10  
  7 purchase totals = $982.32       $1,060.1612   $1,060.16   $1,060.15   $1,060.10