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 $90.25   5.580%   $95.286   $95.29   $95.30   $95.30  
  Purchase #2 $239.82   11.523%   $267.4545   $267.45   $267.45   $267.50  
  Purchase #3 $63.35   5.329%   $66.7259   $66.73   $66.75   $66.70  
  Purchase #4 $25.94   12.575%   $29.202   $29.20   $29.20   $29.20  
  Purchase #5 $165.88   6.134%   $176.0551   $176.06   $176.05   $176.10  
  Purchase #6 $182.80   8.222%   $197.8298   $197.83   $197.85   $197.80  
  Purchase #7 $237.67   13.510%   $269.7792   $269.78   $269.80   $269.80  
  7 purchase totals = $1,005.71       $1,102.3325   $1,102.34   $1,102.40   $1,102.40