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 $41.85   4.170%   $43.5951   $43.60   $43.60   $43.60  
  Purchase #2 $214.27   3.541%   $221.8573   $221.86   $221.85   $221.90  
  Purchase #3 $184.35   13.598%   $209.4179   $209.42   $209.40   $209.40  
  Purchase #4 $139.61   12.593%   $157.1911   $157.19   $157.20   $157.20  
  Purchase #5 $195.84   9.493%   $214.4311   $214.43   $214.45   $214.40  
  Purchase #6 $18.27   8.638%   $19.8482   $19.85   $19.85   $19.80  
  Purchase #7 $229.36   4.732%   $240.2133   $240.21   $240.20   $240.20  
  7 purchase totals = $1,023.55       $1,106.5540   $1,106.56   $1,106.55   $1,106.50