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 $88.62   7.405%   $95.1823   $95.18   $95.20   $95.20  
  Purchase #2 $151.43   4.731%   $158.5942   $158.59   $158.60   $158.60  
  Purchase #3 $89.79   10.206%   $98.954   $98.95   $98.95   $99.00  
  Purchase #4 $15.48   8.219%   $16.7523   $16.75   $16.75   $16.80  
  Purchase #5 $180.87   6.717%   $193.019   $193.02   $193.00   $193.00  
  Purchase #6 $117.72   8.779%   $128.0546   $128.05   $128.05   $128.10  
  Purchase #7 $32.99   11.510%   $36.7871   $36.79   $36.80   $36.80  
  7 purchase totals = $676.90       $727.3435   $727.33   $727.35   $727.50