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 $61.58   12.630%   $69.3576   $69.36   $69.35   $69.40  
  Purchase #2 $169.70   4.154%   $176.7493   $176.75   $176.75   $176.70  
  Purchase #3 $174.33   9.166%   $190.3091   $190.31   $190.30   $190.30  
  Purchase #4 $90.74   13.360%   $102.8629   $102.86   $102.85   $102.90  
  Purchase #5 $133.75   8.844%   $145.5789   $145.58   $145.60   $145.60  
  Purchase #6 $198.27   9.299%   $216.7071   $216.71   $216.70   $216.70  
  Purchase #7 $40.75   7.816%   $43.935   $43.94   $43.95   $43.90  
  7 purchase totals = $869.12       $945.4999   $945.51   $945.50   $945.50