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 $213.33   8.803%   $232.1094   $232.11   $232.10   $232.10  
  Purchase #2 $209.62   5.111%   $220.3337   $220.33   $220.35   $220.30  
  Purchase #3 $99.53   11.141%   $110.6186   $110.62   $110.60   $110.60  
  Purchase #4 $157.34   6.417%   $167.4365   $167.44   $167.45   $167.40  
  Purchase #5 $180.65   11.446%   $201.3272   $201.33   $201.35   $201.30  
  Purchase #6 $231.47   12.846%   $261.2046   $261.20   $261.20   $261.20  
  Purchase #7 $169.32   13.373%   $191.9632   $191.96   $191.95   $192.00  
  7 purchase totals = $1,261.26       $1,384.9932   $1,384.99   $1,385.00   $1,384.90