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 $188.95   4.440%   $197.3394   $197.34   $197.35   $197.30  
  Purchase #2 $219.96   6.353%   $233.9341   $233.93   $233.95   $233.90  
  Purchase #3 $45.76   5.670%   $48.3546   $48.35   $48.35   $48.40  
  Purchase #4 $66.68   11.206%   $74.1522   $74.15   $74.15   $74.20  
  Purchase #5 $199.81   12.390%   $224.5665   $224.57   $224.55   $224.60  
  Purchase #6 $93.51   11.345%   $104.1187   $104.12   $104.10   $104.10  
  Purchase #7 $134.99   7.811%   $145.5341   $145.53   $145.55   $145.50  
  7 purchase totals = $949.66       $1,027.9996   $1,027.99   $1,028.00   $1,028.00