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 $211.60   12.293%   $237.612   $237.61   $237.60   $237.60  
  Purchase #2 $72.61   3.165%   $74.9081   $74.91   $74.90   $74.90  
  Purchase #3 $71.85   9.304%   $78.5349   $78.53   $78.55   $78.50  
  Purchase #4 $208.59   5.159%   $219.3512   $219.35   $219.35   $219.40  
  Purchase #5 $203.53   13.826%   $231.6701   $231.67   $231.65   $231.70  
  Purchase #6 $238.63   5.211%   $251.065   $251.07   $251.05   $251.10  
  Purchase #7 $245.88   5.731%   $259.9714   $259.97   $259.95   $260.00  
  7 purchase totals = $1,252.69       $1,353.1127   $1,353.11   $1,353.05   $1,353.20