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 $76.26   11.709%   $85.1893   $85.19   $85.20   $85.20  
  Purchase #2 $233.79   11.332%   $260.2831   $260.28   $260.30   $260.30  
  Purchase #3 $205.72   7.688%   $221.5358   $221.54   $221.55   $221.50  
  Purchase #4 $141.52   9.305%   $154.6884   $154.69   $154.70   $154.70  
  Purchase #5 $249.92   9.541%   $273.7649   $273.76   $273.75   $273.80  
  Purchase #6 $48.51   8.158%   $52.4674   $52.47   $52.45   $52.50  
  Purchase #7 $55.31   6.642%   $58.9837   $58.98   $59.00   $59.00  
  7 purchase totals = $1,011.03       $1,106.9126   $1,106.91   $1,106.95   $1,107.00