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 $178.78   10.736%   $197.9738   $197.97   $197.95   $198.00  
  Purchase #2 $84.39   12.599%   $95.0223   $95.02   $95.00   $95.00  
  Purchase #3 $94.90   5.761%   $100.3672   $100.37   $100.35   $100.40  
  Purchase #4 $192.99   6.696%   $205.9126   $205.91   $205.90   $205.90  
  Purchase #5 $183.76   8.228%   $198.8798   $198.88   $198.90   $198.90  
  Purchase #6 $208.92   4.381%   $218.0728   $218.07   $218.05   $218.10  
  Purchase #7 $91.62   12.780%   $103.329   $103.33   $103.35   $103.30  
  7 purchase totals = $1,035.36       $1,119.5575   $1,119.55   $1,119.50   $1,119.60