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 $102.97   11.654%   $114.9701   $114.97   $114.95   $115.00  
  Purchase #2 $174.35   6.859%   $186.3087   $186.31   $186.30   $186.30  
  Purchase #3 $54.53   4.713%   $57.1   $57.10   $57.10   $57.10  
  Purchase #4 $190.98   3.307%   $197.2957   $197.30   $197.30   $197.30  
  Purchase #5 $106.85   11.786%   $119.4433   $119.44   $119.45   $119.40  
  Purchase #6 $170.52   6.739%   $182.0113   $182.01   $182.00   $182.00  
  Purchase #7 $158.49   5.114%   $166.5952   $166.60   $166.60   $166.60  
  7 purchase totals = $958.69       $1,023.7243   $1,023.73   $1,023.70   $1,023.70