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 $152.62   3.551%   $158.0395   $158.04   $158.05   $158.00  
  Purchase #2 $76.53   7.670%   $82.3999   $82.40   $82.40   $82.40  
  Purchase #3 $244.80   9.547%   $268.1711   $268.17   $268.15   $268.20  
  Purchase #4 $37.74   9.739%   $41.4155   $41.42   $41.40   $41.40  
  Purchase #5 $216.67   11.296%   $241.145   $241.15   $241.15   $241.10  
  Purchase #6 $153.93   7.297%   $165.1623   $165.16   $165.15   $165.20  
  Purchase #7 $52.66   10.524%   $58.2019   $58.20   $58.20   $58.20  
  7 purchase totals = $934.95       $1,014.5352   $1,014.54   $1,014.50   $1,014.50