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 $69.28   9.785%   $76.059   $76.06   $76.05   $76.10  
  Purchase #2 $225.78   13.222%   $255.6326   $255.63   $255.65   $255.60  
  Purchase #3 $41.33   7.708%   $44.5157   $44.52   $44.50   $44.50  
  Purchase #4 $237.65   8.677%   $258.2709   $258.27   $258.25   $258.30  
  Purchase #5 $209.48   5.264%   $220.507   $220.51   $220.50   $220.50  
  Purchase #6 $47.25   3.696%   $48.9964   $49.00   $49.00   $49.00  
  Purchase #7 $147.59   6.745%   $157.5449   $157.54   $157.55   $157.50  
  7 purchase totals = $978.36       $1,061.5265   $1,061.53   $1,061.50   $1,061.50