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 $69.33   10.400%   $76.5403   $76.54   $76.55   $76.50  
  Purchase #2 $177.36   11.593%   $197.9213   $197.92   $197.90   $197.90  
  Purchase #3 $8.59   5.820%   $9.0899   $9.09   $9.10   $9.10  
  Purchase #4 $176.30   3.419%   $182.3277   $182.33   $182.35   $182.30  
  Purchase #5 $14.29   12.350%   $16.0548   $16.05   $16.05   $16.10  
  Purchase #6 $5.65   6.755%   $6.0317   $6.03   $6.05   $6.00  
  Purchase #7 $211.76   6.273%   $225.0437   $225.04   $225.05   $225.00  
  7 purchase totals = $663.28       $713.0094   $713.00   $713.05   $712.90