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 $65.97   9.124%   $71.9891   $71.99   $72.00   $72.00  
  Purchase #2 $232.74   10.415%   $256.9799   $256.98   $257.00   $257.00  
  Purchase #3 $46.25   8.304%   $50.0906   $50.09   $50.10   $50.10  
  Purchase #4 $60.95   4.426%   $63.6476   $63.65   $63.65   $63.60  
  Purchase #5 $206.50   11.348%   $229.9336   $229.93   $229.95   $229.90  
  Purchase #6 $72.34   3.859%   $75.1316   $75.13   $75.15   $75.10  
  Purchase #7 $239.38   11.471%   $266.8393   $266.84   $266.85   $266.80  
  7 purchase totals = $924.13       $1,014.6117   $1,014.61   $1,014.70   $1,014.50