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 $32.48   4.701%   $34.0069   $34.01   $34.00   $34.00  
  Purchase #2 $198.97   9.461%   $217.7946   $217.79   $217.80   $217.80  
  Purchase #3 $68.97   7.347%   $74.0372   $74.04   $74.05   $74.00  
  Purchase #4 $77.37   13.194%   $87.5782   $87.58   $87.60   $87.60  
  Purchase #5 $158.71   7.407%   $170.4656   $170.47   $170.45   $170.50  
  Purchase #6 $164.62   6.169%   $174.7754   $174.78   $174.80   $174.80  
  Purchase #7 $8.97   3.371%   $9.2724   $9.27   $9.25   $9.30  
  7 purchase totals = $710.09       $767.9303   $767.94   $767.95   $768.00