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 $67.46   12.629%   $75.9795   $75.98   $76.00   $76.00  
  Purchase #2 $173.78   11.660%   $194.0427   $194.04   $194.05   $194.00  
  Purchase #3 $104.90   10.802%   $116.2313   $116.23   $116.25   $116.20  
  Purchase #4 $69.61   8.208%   $75.3236   $75.32   $75.30   $75.30  
  Purchase #5 $135.75   12.710%   $153.0038   $153.00   $153.00   $153.00  
  Purchase #6 $208.51   9.858%   $229.0649   $229.06   $229.05   $229.10  
  Purchase #7 $195.79   10.307%   $215.9701   $215.97   $215.95   $216.00  
  7 purchase totals = $955.80       $1,059.6159   $1,059.60   $1,059.60   $1,059.60