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 $197.57   10.474%   $218.2635   $218.26   $218.25   $218.30  
  Purchase #2 $204.59   9.814%   $224.6685   $224.67   $224.65   $224.70  
  Purchase #3 $60.54   3.155%   $62.45   $62.45   $62.45   $62.50  
  Purchase #4 $176.53   8.850%   $192.1529   $192.15   $192.15   $192.20  
  Purchase #5 $179.50   12.491%   $201.9213   $201.92   $201.90   $201.90  
  Purchase #6 $199.85   3.418%   $206.6809   $206.68   $206.70   $206.70  
  Purchase #7 $181.97   7.156%   $194.9918   $194.99   $195.00   $195.00  
  7 purchase totals = $1,200.55       $1,301.1289   $1,301.12   $1,301.10   $1,301.30