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 $94.28   3.539%   $97.6166   $97.62   $97.60   $97.60  
  Purchase #2 $199.63   3.270%   $206.1579   $206.16   $206.15   $206.20  
  Purchase #3 $90.30   9.188%   $98.5968   $98.60   $98.60   $98.60  
  Purchase #4 $94.82   9.414%   $103.7464   $103.75   $103.75   $103.70  
  Purchase #5 $140.64   8.572%   $152.6957   $152.70   $152.70   $152.70  
  Purchase #6 $213.35   11.301%   $237.4607   $237.46   $237.45   $237.50  
  Purchase #7 $147.95   13.162%   $167.4232   $167.42   $167.40   $167.40  
  7 purchase totals = $980.97       $1,063.6973   $1,063.71   $1,063.65   $1,063.70