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 $85.77   11.168%   $95.3488   $95.35   $95.35   $95.30  
  Purchase #2 $128.90   7.475%   $138.5353   $138.54   $138.55   $138.50  
  Purchase #3 $61.48   7.683%   $66.2035   $66.20   $66.20   $66.20  
  Purchase #4 $43.34   6.671%   $46.2312   $46.23   $46.25   $46.20  
  Purchase #5 $104.90   5.816%   $111.001   $111.00   $111.00   $111.00  
  Purchase #6 $148.93   7.822%   $160.5793   $160.58   $160.60   $160.60  
  Purchase #7 $155.95   13.781%   $177.4415   $177.44   $177.45   $177.40  
  7 purchase totals = $729.27       $795.3406   $795.34   $795.40   $795.20