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 $68.47   5.157%   $72.001   $72.00   $72.00   $72.00  
  Purchase #2 $194.69   3.680%   $201.8546   $201.85   $201.85   $201.90  
  Purchase #3 $33.29   8.543%   $36.134   $36.13   $36.15   $36.10  
  Purchase #4 $65.84   11.494%   $73.4076   $73.41   $73.40   $73.40  
  Purchase #5 $71.84   4.273%   $74.9097   $74.91   $74.90   $74.90  
  Purchase #6 $234.25   12.222%   $262.88   $262.88   $262.90   $262.90  
  Purchase #7 $192.80   8.675%   $209.5254   $209.53   $209.55   $209.50  
  7 purchase totals = $861.18       $930.7123   $930.71   $930.75   $930.70