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 $216.42   11.639%   $241.6091   $241.61   $241.60   $241.60  
  Purchase #2 $152.81   6.330%   $162.4829   $162.48   $162.50   $162.50  
  Purchase #3 $178.87   7.320%   $191.9633   $191.96   $191.95   $192.00  
  Purchase #4 $68.26   11.325%   $75.9904   $75.99   $76.00   $76.00  
  Purchase #5 $157.64   5.281%   $165.965   $165.97   $165.95   $166.00  
  Purchase #6 $167.35   9.437%   $183.1428   $183.14   $183.15   $183.10  
  Purchase #7 $167.55   8.333%   $181.5119   $181.51   $181.50   $181.50  
  7 purchase totals = $1,108.90       $1,202.6654   $1,202.66   $1,202.65   $1,202.70