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 $176.81   11.841%   $197.7461   $197.75   $197.75   $197.70  
  Purchase #2 $207.26   10.809%   $229.6627   $229.66   $229.65   $229.70  
  Purchase #3 $15.25   5.170%   $16.0384   $16.04   $16.05   $16.00  
  Purchase #4 $153.66   8.707%   $167.0392   $167.04   $167.05   $167.00  
  Purchase #5 $48.54   3.568%   $50.2719   $50.27   $50.25   $50.30  
  Purchase #6 $215.76   9.182%   $235.5711   $235.57   $235.55   $235.60  
  Purchase #7 $117.65   12.709%   $132.6021   $132.60   $132.60   $132.60  
  7 purchase totals = $934.93       $1,028.9315   $1,028.93   $1,028.90   $1,028.90