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 $61.47   13.825%   $69.9682   $69.97   $69.95   $70.00  
  Purchase #2 $229.94   12.300%   $258.2226   $258.22   $258.20   $258.20  
  Purchase #3 $65.65   6.679%   $70.0348   $70.03   $70.05   $70.00  
  Purchase #4 $50.79   8.711%   $55.2143   $55.21   $55.20   $55.20  
  Purchase #5 $87.62   8.352%   $94.938   $94.94   $94.95   $94.90  
  Purchase #6 $238.73   11.432%   $266.0216   $266.02   $266.00   $266.00  
  Purchase #7 $173.64   12.722%   $195.7305   $195.73   $195.75   $195.70  
  7 purchase totals = $907.84       $1,010.1300   $1,010.12   $1,010.10   $1,010.00