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 $56.55   10.864%   $62.6936   $62.69   $62.70   $62.70  
  Purchase #2 $67.86   7.506%   $72.9536   $72.95   $72.95   $73.00  
  Purchase #3 $65.97   12.541%   $74.2433   $74.24   $74.25   $74.20  
  Purchase #4 $166.99   7.829%   $180.0636   $180.06   $180.05   $180.10  
  Purchase #5 $207.85   6.325%   $220.9965   $221.00   $221.00   $221.00  
  Purchase #6 $178.40   7.169%   $191.1895   $191.19   $191.20   $191.20  
  Purchase #7 $206.91   3.180%   $213.4897   $213.49   $213.50   $213.50  
  7 purchase totals = $950.53       $1,015.6298   $1,015.62   $1,015.65   $1,015.70