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 $58.94   5.725%   $62.3143   $62.31   $62.30   $62.30  
  Purchase #2 $181.53   9.213%   $198.2544   $198.25   $198.25   $198.30  
  Purchase #3 $238.64   8.674%   $259.3396   $259.34   $259.35   $259.30  
  Purchase #4 $84.35   9.605%   $92.4518   $92.45   $92.45   $92.50  
  Purchase #5 $201.91   9.853%   $221.8042   $221.80   $221.80   $221.80  
  Purchase #6 $64.68   8.396%   $70.1105   $70.11   $70.10   $70.10  
  Purchase #7 $206.78   11.483%   $230.5245   $230.52   $230.50   $230.50  
  7 purchase totals = $1,036.83       $1,134.7993   $1,134.78   $1,134.75   $1,134.80