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 $198.97   8.536%   $215.9541   $215.95   $215.95   $216.00  
  Purchase #2 $221.66   10.377%   $244.6617   $244.66   $244.65   $244.70  
  Purchase #3 $39.88   10.398%   $44.0267   $44.03   $44.05   $44.00  
  Purchase #4 $160.44   4.220%   $167.2106   $167.21   $167.20   $167.20  
  Purchase #5 $79.51   7.665%   $85.6044   $85.60   $85.60   $85.60  
  Purchase #6 $242.84   9.538%   $266.0021   $266.00   $266.00   $266.00  
  Purchase #7 $39.98   9.531%   $43.7905   $43.79   $43.80   $43.80  
  7 purchase totals = $983.28       $1,067.2501   $1,067.24   $1,067.25   $1,067.30