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 $96.37   4.759%   $100.9562   $100.96   $100.95   $101.00  
  Purchase #2 $158.57   11.126%   $176.2125   $176.21   $176.20   $176.20  
  Purchase #3 $147.86   9.728%   $162.2438   $162.24   $162.25   $162.20  
  Purchase #4 $228.76   7.833%   $246.6788   $246.68   $246.70   $246.70  
  Purchase #5 $83.81   6.801%   $89.5099   $89.51   $89.50   $89.50  
  Purchase #6 $59.25   11.752%   $66.2131   $66.21   $66.20   $66.20  
  Purchase #7 $55.81   7.823%   $60.176   $60.18   $60.20   $60.20  
  7 purchase totals = $830.43       $901.9903   $901.99   $902.00   $902.00