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 $118.51   12.671%   $133.5264   $133.53   $133.55   $133.50  
  Purchase #2 $118.92   10.820%   $131.7871   $131.79   $131.80   $131.80  
  Purchase #3 $103.56   10.300%   $114.2267   $114.23   $114.25   $114.20  
  Purchase #4 $90.87   5.645%   $95.9996   $96.00   $96.00   $96.00  
  Purchase #5 $162.34   5.288%   $170.9245   $170.92   $170.90   $170.90  
  Purchase #6 $186.97   9.288%   $204.3358   $204.34   $204.35   $204.30  
  Purchase #7 $152.67   7.400%   $163.9676   $163.97   $163.95   $164.00  
  7 purchase totals = $933.84       $1,014.7677   $1,014.78   $1,014.80   $1,014.70