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 $236.65   10.723%   $262.026   $262.03   $262.05   $262.00  
  Purchase #2 $89.53   12.772%   $100.9648   $100.96   $100.95   $101.00  
  Purchase #3 $136.57   9.596%   $149.6753   $149.68   $149.70   $149.70  
  Purchase #4 $110.96   5.745%   $117.3347   $117.33   $117.35   $117.30  
  Purchase #5 $170.57   12.132%   $191.2636   $191.26   $191.25   $191.30  
  Purchase #6 $31.26   13.255%   $35.4035   $35.40   $35.40   $35.40  
  Purchase #7 $244.42   4.576%   $255.6047   $255.60   $255.60   $255.60  
  7 purchase totals = $1,019.96       $1,112.2726   $1,112.26   $1,112.30   $1,112.30