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 $152.75   11.244%   $169.9252   $169.93   $169.95   $169.90  
  Purchase #2 $71.83   6.780%   $76.7001   $76.70   $76.70   $76.70  
  Purchase #3 $90.67   12.176%   $101.71   $101.71   $101.70   $101.70  
  Purchase #4 $197.50   8.399%   $214.088   $214.09   $214.10   $214.10  
  Purchase #5 $155.41   9.123%   $169.5881   $169.59   $169.60   $169.60  
  Purchase #6 $246.59   6.736%   $263.2003   $263.20   $263.20   $263.20  
  Purchase #7 $168.42   6.581%   $179.5037   $179.50   $179.50   $179.50  
  7 purchase totals = $1,083.17       $1,174.7154   $1,174.72   $1,174.75   $1,174.70