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 $244.37   7.514%   $262.732   $262.73   $262.75   $262.70  
  Purchase #2 $84.45   3.173%   $87.1296   $87.13   $87.15   $87.10  
  Purchase #3 $41.38   11.108%   $45.9765   $45.98   $46.00   $46.00  
  Purchase #4 $81.30   4.606%   $85.0447   $85.04   $85.05   $85.00  
  Purchase #5 $5.62   3.579%   $5.8211   $5.82   $5.80   $5.80  
  Purchase #6 $211.29   4.594%   $220.9967   $221.00   $221.00   $221.00  
  Purchase #7 $146.50   7.342%   $157.256   $157.26   $157.25   $157.30  
  7 purchase totals = $814.91       $864.9566   $864.96   $865.00   $864.90